Discussion:
User Activated Soft Fork Split Protection
(too old to reply)
James Hilliard via bitcoin-dev
2017-06-07 00:56:10 UTC
Permalink
Raw Message
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.

The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.

This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.

<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Author: James Hilliard <***@gmail.com>
Comments-Summary: No comments yet.
Comments-URI:
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>

==Abstract==

This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.

==Definitions==

"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.

==Motivation==

The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.

This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.

==Specification==

While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.

==Deployment==

This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.

This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.

=== Reference implementation ===

<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}

// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}

// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>

https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1

==Backwards Compatibility==

This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.

==Rationale==

Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.

By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.

==References==

*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]

==Copyright==

This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
Karl Johan Alm via bitcoin-dev
2017-06-07 01:11:25 UTC
Permalink
Raw Message
One thing about BIP148 activation that may be affected by this is the
fact that segwit signalling non-BIP148 miners + BIP148 miners may hold
majority hash power and prevent a chain split. With this SF, that will
no longer be the case, right? Or am I completely confused on the
subject?

On Wed, Jun 7, 2017 at 9:56 AM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-07 01:29:18 UTC
Permalink
Raw Message
You need a majority of miners enforcing BIP148 upon BIP148 activation
to prevent a split, not just a majority signalling segwit. This
provides a miner coordination mechanism for BIP148 mandatory
signalling enforcement.

On Tue, Jun 6, 2017 at 8:11 PM, Karl Johan Alm
Post by Karl Johan Alm via bitcoin-dev
One thing about BIP148 activation that may be affected by this is the
fact that segwit signalling non-BIP148 miners + BIP148 miners may hold
majority hash power and prevent a chain split. With this SF, that will
no longer be the case, right? Or am I completely confused on the
subject?
On Wed, Jun 7, 2017 at 9:56 AM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-07 01:54:37 UTC
Permalink
Raw Message
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-07 10:13:43 UTC
Permalink
Raw Message
I think even 55% would probably work out fine simply due to incentive
structures, once signalling is over 51% it's then clear to miners that
non-signalling blocks will be orphaned and the rest will rapidly
update to splitprotection/BIP148. The purpose of this BIP is to reduce
chain split risk for BIP148 since it's looking like BIP148 is going to
be run by a non-insignificant percentage of the economy at a minimum.
See thread on replay attacks for why activating regardless of threshold is a
bad idea [1].
BIP91 OTOH seems perfectly reasonable. 80% instead of 95% makes it more
difficult for miners to hold together in opposition to Core. It gives Core
more leverage in negotiations.
If they don't activate with 80%, Core can release another BIP to reduce it
to 75%.
Each threshold reduction makes it both more likely to succeed, but also
increases the likelihood of harm to the ecosystem.
Cheers,
Greg
[1]
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-June/014497.html
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Erik Aronesty via bitcoin-dev
2017-06-07 14:10:48 UTC
Permalink
Raw Message
This is, by far, the safest way for miners to quickly defend against a
chain split, much better than a -bip148 option. This allows miners to
defend themselves, with very little risk, since the defense is only
activated if the majority of miners do so. I would move for a very rapid
deployment. Only miners would need to upgrade. Regular users would not
have to concern themselves with this release.

On Wed, Jun 7, 2017 at 6:13 AM, James Hilliard via bitcoin-dev <
Post by James Hilliard via bitcoin-dev
I think even 55% would probably work out fine simply due to incentive
structures, once signalling is over 51% it's then clear to miners that
non-signalling blocks will be orphaned and the rest will rapidly
update to splitprotection/BIP148. The purpose of this BIP is to reduce
chain split risk for BIP148 since it's looking like BIP148 is going to
be run by a non-insignificant percentage of the economy at a minimum.
See thread on replay attacks for why activating regardless of threshold
is a
bad idea [1].
BIP91 OTOH seems perfectly reasonable. 80% instead of 95% makes it more
difficult for miners to hold together in opposition to Core. It gives
Core
more leverage in negotiations.
If they don't activate with 80%, Core can release another BIP to reduce
it
to 75%.
Each threshold reduction makes it both more likely to succeed, but also
increases the likelihood of harm to the ecosystem.
Cheers,
Greg
[1]
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/
2017-June/014497.html
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...
jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/
bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.
cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Jacob Eliosoff via bitcoin-dev
2017-06-07 16:44:32 UTC
Permalink
Raw Message
This is not the safest defense against a split. If 70% of miners run
"splitprotection", and 0.1% run BIP148, there's no "safety"/"defense"
reason for splitprotection to activate segwit. It should only do so if
*BIP148* support (NB: not just segwit support!) >50%.

The truly defensive logic is "If the majority supports orphaning non-segwit
blocks starting Aug 1, I'll join them."

If the real goal of this BIP is to induce miners to run segwit, then fair
enough. But passing it off as the safest defense is bad faith.


On Wed, Jun 7, 2017 at 10:10 AM, Erik Aronesty via bitcoin-dev <
Post by Erik Aronesty via bitcoin-dev
This is, by far, the safest way for miners to quickly defend against a
chain split, much better than a -bip148 option. This allows miners to
defend themselves, with very little risk, since the defense is only
activated if the majority of miners do so. I would move for a very rapid
deployment. Only miners would need to upgrade. Regular users would not
have to concern themselves with this release.
On Wed, Jun 7, 2017 at 6:13 AM, James Hilliard via bitcoin-dev <
Post by James Hilliard via bitcoin-dev
I think even 55% would probably work out fine simply due to incentive
structures, once signalling is over 51% it's then clear to miners that
non-signalling blocks will be orphaned and the rest will rapidly
update to splitprotection/BIP148. The purpose of this BIP is to reduce
chain split risk for BIP148 since it's looking like BIP148 is going to
be run by a non-insignificant percentage of the economy at a minimum.
See thread on replay attacks for why activating regardless of threshold
is a
bad idea [1].
BIP91 OTOH seems perfectly reasonable. 80% instead of 95% makes it more
difficult for miners to hold together in opposition to Core. It gives
Core
more leverage in negotiations.
If they don't activate with 80%, Core can release another BIP to reduce
it
to 75%.
Each threshold reduction makes it both more likely to succeed, but also
increases the likelihood of harm to the ecosystem.
Cheers,
Greg
[1]
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017
-June/014497.html
--
Please do not email me anything that you are not comfortable also
sharing
with the NSA.
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential
havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also
sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilli
ard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/
2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cp
p#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Erik Aronesty via bitcoin-dev
2017-06-07 18:05:52 UTC
Permalink
Raw Message
Post by Jacob Eliosoff via bitcoin-dev
But passing it off as the safest defense is bad faith.
Without this option, a miner has to guess whether a split will be
economically impacting. With this option, his miner will automatically
switch to the chain least likely to get wiped out... as soon as a simple
majority of miners supports it.
Post by Jacob Eliosoff via bitcoin-dev
This is not the safest defense against a split. If 70% of miners run
"splitprotection", and 0.1% run BIP148, there's no "safety"/"defense"
reason for splitprotection to activate segwit. It should only do so if
*BIP148* support (NB: not just segwit support!) >50%.
The truly defensive logic is "If the majority supports orphaning
non-segwit blocks starting Aug 1, I'll join them."
If the real goal of this BIP is to induce miners to run segwit, then fair
enough. But passing it off as the safest defense is bad faith.
On Wed, Jun 7, 2017 at 10:10 AM, Erik Aronesty via bitcoin-dev <
Post by Erik Aronesty via bitcoin-dev
This is, by far, the safest way for miners to quickly defend against a
chain split, much better than a -bip148 option. This allows miners to
defend themselves, with very little risk, since the defense is only
activated if the majority of miners do so. I would move for a very rapid
deployment. Only miners would need to upgrade. Regular users would not
have to concern themselves with this release.
On Wed, Jun 7, 2017 at 6:13 AM, James Hilliard via bitcoin-dev <
Post by James Hilliard via bitcoin-dev
I think even 55% would probably work out fine simply due to incentive
structures, once signalling is over 51% it's then clear to miners that
non-signalling blocks will be orphaned and the rest will rapidly
update to splitprotection/BIP148. The purpose of this BIP is to reduce
chain split risk for BIP148 since it's looking like BIP148 is going to
be run by a non-insignificant percentage of the economy at a minimum.
See thread on replay attacks for why activating regardless of
threshold is a
bad idea [1].
BIP91 OTOH seems perfectly reasonable. 80% instead of 95% makes it more
difficult for miners to hold together in opposition to Core. It gives
Core
more leverage in negotiations.
If they don't activate with 80%, Core can release another BIP to
reduce it
to 75%.
Each threshold reduction makes it both more likely to succeed, but also
increases the likelihood of harm to the ecosystem.
Cheers,
Greg
[1]
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017
-June/014497.html
--
Please do not email me anything that you are not comfortable also
sharing
with the NSA.
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential
havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also
sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00
UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilli
ard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/20
17-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cp
p#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit
deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Jacob Eliosoff via bitcoin-dev
2017-06-07 19:39:48 UTC
Permalink
Raw Message
You're missing my point. "As soon as a simple majority supports it" - what
is "it"? BIP148? Or "deferring to the miner consensus on BIP148"? It's
the difference between supporting one side of a vote, vs supporting
deferral to the outcome of the vote.

Or if you mean, the safe thing for miners is to orphan non-segwit blocks
Aug 1 *regardless* of the miner consensus (since the economic consensus
might differ), then there's zero need for this BIP: they should just run
BIP148.

As I said: this BIP should be corrected to only orphan if >50% signal for
BIP148. Or, define two bits, one meaning "I support BIP148," the other "I
will go w/ the miner majority on BIP148." Fudging them this way is
deceptive.
Post by Jacob Eliosoff via bitcoin-dev
But passing it off as the safest defense is bad faith.
Without this option, a miner has to guess whether a split will be
economically impacting. With this option, his miner will automatically
switch to the chain least likely to get wiped out... as soon as a simple
majority of miners supports it.
Post by Jacob Eliosoff via bitcoin-dev
This is not the safest defense against a split. If 70% of miners run
"splitprotection", and 0.1% run BIP148, there's no "safety"/"defense"
reason for splitprotection to activate segwit. It should only do so if
*BIP148* support (NB: not just segwit support!) >50%.
The truly defensive logic is "If the majority supports orphaning
non-segwit blocks starting Aug 1, I'll join them."
If the real goal of this BIP is to induce miners to run segwit, then fair
enough. But passing it off as the safest defense is bad faith.
On Wed, Jun 7, 2017 at 10:10 AM, Erik Aronesty via bitcoin-dev <
Post by Erik Aronesty via bitcoin-dev
This is, by far, the safest way for miners to quickly defend against a
chain split, much better than a -bip148 option. This allows miners to
defend themselves, with very little risk, since the defense is only
activated if the majority of miners do so. I would move for a very rapid
deployment. Only miners would need to upgrade. Regular users would not
have to concern themselves with this release.
On Wed, Jun 7, 2017 at 6:13 AM, James Hilliard via bitcoin-dev <
Post by James Hilliard via bitcoin-dev
I think even 55% would probably work out fine simply due to incentive
structures, once signalling is over 51% it's then clear to miners that
non-signalling blocks will be orphaned and the rest will rapidly
update to splitprotection/BIP148. The purpose of this BIP is to reduce
chain split risk for BIP148 since it's looking like BIP148 is going to
be run by a non-insignificant percentage of the economy at a minimum.
See thread on replay attacks for why activating regardless of
threshold is a
bad idea [1].
BIP91 OTOH seems perfectly reasonable. 80% instead of 95% makes it more
difficult for miners to hold together in opposition to Core. It gives
Core
more leverage in negotiations.
If they don't activate with 80%, Core can release another BIP to
reduce it
to 75%.
Each threshold reduction makes it both more likely to succeed, but also
increases the likelihood of harm to the ecosystem.
Cheers,
Greg
[1]
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017
-June/014497.html
--
Please do not email me anything that you are not comfortable also
sharing
with the NSA.
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential
havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also
sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00
UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilli
ard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/20
17-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cp
p#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit
deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Erik Aronesty via bitcoin-dev
2017-06-07 19:59:23 UTC
Permalink
Raw Message
I get it, a threshold could be put in place, but something like 33% would
more accurately reflect the risks miners run.

I'm not aware of a good signal to indicates someone is planning to run
BIP148 and orphan a miner's blocks.
Post by Jacob Eliosoff via bitcoin-dev
You're missing my point. "As soon as a simple majority supports it" -
what is "it"? BIP148? Or "deferring to the miner consensus on BIP148"?
It's the difference between supporting one side of a vote, vs supporting
deferral to the outcome of the vote.
Or if you mean, the safe thing for miners is to orphan non-segwit blocks
Aug 1 *regardless* of the miner consensus (since the economic consensus
might differ), then there's zero need for this BIP: they should just run
BIP148.
As I said: this BIP should be corrected to only orphan if >50% signal for
BIP148. Or, define two bits, one meaning "I support BIP148," the other "I
will go w/ the miner majority on BIP148." Fudging them this way is
deceptive.
Post by Jacob Eliosoff via bitcoin-dev
But passing it off as the safest defense is bad faith.
Without this option, a miner has to guess whether a split will be
economically impacting. With this option, his miner will automatically
switch to the chain least likely to get wiped out... as soon as a simple
majority of miners supports it.
Post by Jacob Eliosoff via bitcoin-dev
This is not the safest defense against a split. If 70% of miners run
"splitprotection", and 0.1% run BIP148, there's no "safety"/"defense"
reason for splitprotection to activate segwit. It should only do so if
*BIP148* support (NB: not just segwit support!) >50%.
The truly defensive logic is "If the majority supports orphaning
non-segwit blocks starting Aug 1, I'll join them."
If the real goal of this BIP is to induce miners to run segwit, then fair
enough. But passing it off as the safest defense is bad faith.
On Wed, Jun 7, 2017 at 10:10 AM, Erik Aronesty via bitcoin-dev <
Post by Erik Aronesty via bitcoin-dev
This is, by far, the safest way for miners to quickly defend against a
chain split, much better than a -bip148 option. This allows miners to
defend themselves, with very little risk, since the defense is only
activated if the majority of miners do so. I would move for a very rapid
deployment. Only miners would need to upgrade. Regular users would not
have to concern themselves with this release.
On Wed, Jun 7, 2017 at 6:13 AM, James Hilliard via bitcoin-dev <
Post by James Hilliard via bitcoin-dev
I think even 55% would probably work out fine simply due to incentive
structures, once signalling is over 51% it's then clear to miners that
non-signalling blocks will be orphaned and the rest will rapidly
update to splitprotection/BIP148. The purpose of this BIP is to reduce
chain split risk for BIP148 since it's looking like BIP148 is going to
be run by a non-insignificant percentage of the economy at a minimum.
See thread on replay attacks for why activating regardless of
threshold is a
bad idea [1].
BIP91 OTOH seems perfectly reasonable. 80% instead of 95% makes it
more
difficult for miners to hold together in opposition to Core. It gives
Core
more leverage in negotiations.
If they don't activate with 80%, Core can release another BIP to
reduce it
to 75%.
Each threshold reduction makes it both more likely to succeed, but
also
increases the likelihood of harm to the ecosystem.
Cheers,
Greg
[1]
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017
-June/014497.html
--
Please do not email me anything that you are not comfortable also
sharing
with the NSA.
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow
a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential
havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also
sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00
UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilli
ard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/20
17-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cp
p#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit
deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-07 21:21:29 UTC
Permalink
Raw Message
Keep in mind that this is only temporary until segwit has locked in,
after that happens it becomes optional for miners again.
This is, by far, the safest way for miners to quickly defend against a chain split, much better than a -bip148 option. This allows miners to defend themselves, with very little risk, since the defense is only activated if the majority of miners do so. I would move for a very rapid deployment. Only miners would need to upgrade. Regular users would not have to concern themselves with this release.
FYI, even if very successful, this deployment and change may have a
severe negative impact on a small group of miners. Any miners/pools
who are not actively following the forums, news, or these discussions
may be difficult to reach and communicate with in time, particularly
with language barriers. Of those, any who are also either not
signaling segwit currently or are running an older software version
will have their blocks continuously and constantly orphaned, but may
not have any alarms or notifications set up for such an unexpected
failure. That may or may not be a worthy consideration, but it is
definitely brusque and a harsh price to pay. Considering the
opposition mentioned against transaction limits for the rare cases
where a very large transaction has already been signed, it seems that
this would be worthy of consideration. For the few miners in that
situation, it does turn segwit from an optional softfork into a
punishing hardfork.
I don't think that's a sufficient reason alone to kill the idea, but
it should be a concern.
Jared
On Wed, Jun 7, 2017 at 7:10 AM, Erik Aronesty via bitcoin-dev
This is, by far, the safest way for miners to quickly defend against a chain
split, much better than a -bip148 option. This allows miners to defend
themselves, with very little risk, since the defense is only activated if
the majority of miners do so. I would move for a very rapid deployment.
Only miners would need to upgrade. Regular users would not have to concern
themselves with this release.
On Wed, Jun 7, 2017 at 6:13 AM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
I think even 55% would probably work out fine simply due to incentive
structures, once signalling is over 51% it's then clear to miners that
non-signalling blocks will be orphaned and the rest will rapidly
update to splitprotection/BIP148. The purpose of this BIP is to reduce
chain split risk for BIP148 since it's looking like BIP148 is going to
be run by a non-insignificant percentage of the economy at a minimum.
See thread on replay attacks for why activating regardless of threshold is a
bad idea [1].
BIP91 OTOH seems perfectly reasonable. 80% instead of 95% makes it more
difficult for miners to hold together in opposition to Core. It gives Core
more leverage in negotiations.
If they don't activate with 80%, Core can release another BIP to reduce it
to 75%.
Each threshold reduction makes it both more likely to succeed, but also
increases the likelihood of harm to the ecosystem.
Cheers,
Greg
[1]
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-June/014497.html
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-07 21:44:52 UTC
Permalink
Raw Message
Yes, this is the same as BIP148, there is no mandatory signalling
after segwit is locked in.
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Keep in mind that this is only temporary until segwit has locked in,
after that happens it becomes optional for miners again.
I missed that, that does effectively address that concern. It appears
that BIP148 implements the same rule as would be required to prevent a
later chainsplit as well, no?
This comment did bring to mind another concern about BIP148/91 though,
which I'll raise in the pull request discussion. Feel free to respond
to it there.
Jared
On Wed, Jun 7, 2017 at 2:21 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
Keep in mind that this is only temporary until segwit has locked in,
after that happens it becomes optional for miners again.
This is, by far, the safest way for miners to quickly defend against a chain split, much better than a -bip148 option. This allows miners to defend themselves, with very little risk, since the defense is only activated if the majority of miners do so. I would move for a very rapid deployment. Only miners would need to upgrade. Regular users would not have to concern themselves with this release.
FYI, even if very successful, this deployment and change may have a
severe negative impact on a small group of miners. Any miners/pools
who are not actively following the forums, news, or these discussions
may be difficult to reach and communicate with in time, particularly
with language barriers. Of those, any who are also either not
signaling segwit currently or are running an older software version
will have their blocks continuously and constantly orphaned, but may
not have any alarms or notifications set up for such an unexpected
failure. That may or may not be a worthy consideration, but it is
definitely brusque and a harsh price to pay. Considering the
opposition mentioned against transaction limits for the rare cases
where a very large transaction has already been signed, it seems that
this would be worthy of consideration. For the few miners in that
situation, it does turn segwit from an optional softfork into a
punishing hardfork.
I don't think that's a sufficient reason alone to kill the idea, but
it should be a concern.
Jared
On Wed, Jun 7, 2017 at 7:10 AM, Erik Aronesty via bitcoin-dev
This is, by far, the safest way for miners to quickly defend against a chain
split, much better than a -bip148 option. This allows miners to defend
themselves, with very little risk, since the defense is only activated if
the majority of miners do so. I would move for a very rapid deployment.
Only miners would need to upgrade. Regular users would not have to concern
themselves with this release.
On Wed, Jun 7, 2017 at 6:13 AM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
I think even 55% would probably work out fine simply due to incentive
structures, once signalling is over 51% it's then clear to miners that
non-signalling blocks will be orphaned and the rest will rapidly
update to splitprotection/BIP148. The purpose of this BIP is to reduce
chain split risk for BIP148 since it's looking like BIP148 is going to
be run by a non-insignificant percentage of the economy at a minimum.
See thread on replay attacks for why activating regardless of threshold is a
bad idea [1].
BIP91 OTOH seems perfectly reasonable. 80% instead of 95% makes it more
difficult for miners to hold together in opposition to Core. It gives Core
more leverage in negotiations.
If they don't activate with 80%, Core can release another BIP to reduce it
to 75%.
Each threshold reduction makes it both more likely to succeed, but also
increases the likelihood of harm to the ecosystem.
Cheers,
Greg
[1]
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-June/014497.html
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Jacob Eliosoff via bitcoin-dev
2017-06-07 04:17:37 UTC
Permalink
Raw Message
While this isn't an unreasonable proposal, it will orphan blocks from any
miner who isn't running it (or BIP148) by Aug 1, right? That seems rather
rushed for a non-backwards-compatible SF, especially since in practice,
miners are unlikely to deploy it until it comes bundled with some version
of the Segwit2x HF code.

I realize this is a touchy topic but - how much hard evidence is there that
there *will* be significant disruption if miners simply ignore both this
and BIP148? Correct me but afaict, BIP148 has ~0% hashrate support.

Unless the HF code is ready and agree on soon (say by Jul 1), my vote is to
keep the main chain backwards-compatible, especially if evidence of miner
support for BIP148 doesn't materialize soon. It seems less disruptive for
recently-deployed BIP148 nodes to revert than to ask every miner in the
system to quickly upgrade or get orphaned.

Just my view, I respect that others will differ.


On Tue, Jun 6, 2017 at 9:54 PM, James Hilliard via bitcoin-dev <
Post by James Hilliard via bitcoin-dev
This is a BIP8 style soft fork so mandatory signalling will be active
after Aug 1st regardless.
What is the probability that a 65% threshold is too low and can allow a
"surprise miner attack", whereby miners are kept offline before the
deadline, and brought online immediately after, creating potential havoc?
(Nit: "simple majority" usually refers to >50%, I think, might cause
confusion.)
-Greg Slepak
--
Please do not email me anything that you are not comfortable also sharing
with the NSA.
On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...
jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/
bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.
cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-07 21:42:52 UTC
Permalink
Raw Message
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to provide a
risk mitigation measure that miners can safely deploy. Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split. At this point it is not completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until BIP148
activation. I intentionally used a shorter activation period here so
that decisions by miners can be made close to the BIP148 activation
date.
I think this BIP represents a gamble, and the gamble may not be a good
one. The gamble here is that if the segwit2x changes are rolled out
on time, and if the signatories accept the bit4 + bit1 signaling
proposals within BIP91, the launch will go smoother, as intended. But
conversely, if either the segwit2x signatories balk about the Bit1
signaling OR if the timelines for segwit2mb are missed even by a bit,
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble to be
making.
The reason I say it may make the chainsplit be worse than it would
otherwise be is that it may provide a false sense of safety for BIP148
that currently does not currently exist(and should not, as it is a
chainsplit). That sense of safety would only be legitimate if the
segwit2x signatories were on board, and the segwit2x code effectively
enforced BIP148 simultaneously, neither of which are guaranteed. If
users and more miners had a false sense that BIP148 was *not* going to
chainsplit from default / segwit2x, they might not follow the news if
suddenly the segwit2x plan were delayed for a few days. While any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal would
take BIP148 from the "unlikely to have any viable chain after flag day
without segwit2x" category into the "small but viable minority chain"
category, and even worse, it might strengthen the chainsplit just days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the client,
and if BIP148 support were much much broader, I would feel differently
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it (by
strengthening an extreme minority chainsplit that may wind up on the
wrong side of two segwit-activated chains). As it stands now, this
seems like a very dangerous attempt to compromise with a small but
vocal group that are the ones creating the threat to begin with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Jared Lee Richardson via bitcoin-dev
2017-06-07 21:50:18 UTC
Permalink
Raw Message
Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?

The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a more
standard approach to activation that requires stronger consensus and
may be more forgiving than BIP148. If the segwit2x activation is on
time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on that
idea? It may add more complexity and more developer time, but may
also address your concerns among others.
Post by James Hilliard via bitcoin-dev
Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving BIP148
a sense of safety that may not be valid. Without several more steps,
BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain. (Unless
the segwit2x compromise falls apart before then, and even in that case
it is likely to be a minority chain)

Jared


On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to provide a
risk mitigation measure that miners can safely deploy. Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split. At this point it is not completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until BIP148
activation. I intentionally used a shorter activation period here so
that decisions by miners can be made close to the BIP148 activation
date.
I think this BIP represents a gamble, and the gamble may not be a good
one. The gamble here is that if the segwit2x changes are rolled out
on time, and if the signatories accept the bit4 + bit1 signaling
proposals within BIP91, the launch will go smoother, as intended. But
conversely, if either the segwit2x signatories balk about the Bit1
signaling OR if the timelines for segwit2mb are missed even by a bit,
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble to be
making.
The reason I say it may make the chainsplit be worse than it would
otherwise be is that it may provide a false sense of safety for BIP148
that currently does not currently exist(and should not, as it is a
chainsplit). That sense of safety would only be legitimate if the
segwit2x signatories were on board, and the segwit2x code effectively
enforced BIP148 simultaneously, neither of which are guaranteed. If
users and more miners had a false sense that BIP148 was *not* going to
chainsplit from default / segwit2x, they might not follow the news if
suddenly the segwit2x plan were delayed for a few days. While any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal would
take BIP148 from the "unlikely to have any viable chain after flag day
without segwit2x" category into the "small but viable minority chain"
category, and even worse, it might strengthen the chainsplit just days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the client,
and if BIP148 support were much much broader, I would feel differently
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it (by
strengthening an extreme minority chainsplit that may wind up on the
wrong side of two segwit-activated chains). As it stands now, this
seems like a very dangerous attempt to compromise with a small but
vocal group that are the ones creating the threat to begin with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-07 22:23:31 UTC
Permalink
Raw Message
Post by Jared Lee Richardson via bitcoin-dev
Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?
It's fairly trivial for miners to signal for BIP91 on bit4 or a
different bit at the same time as the code is trivial enough to
combine
Post by Jared Lee Richardson via bitcoin-dev
The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a more
standard approach to activation that requires stronger consensus and
may be more forgiving than BIP148. If the segwit2x activation is on
time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on that
idea? It may add more complexity and more developer time, but may
also address your concerns among others.
This does give miners another approach to activate segwit ahead of
BIP148, if segwit2x activation is rolled out and activated immediately
then this would not be needed however based on the timeline here
https://segwit2x.github.io/ it would not be possible for BIP91 to
enforce mandatory signalling ahead of BIP148. Maybe that can be
changed though, I've suggested an immediate rollout with a placeholder
client timeout instead of the HF code initially in order to accelerate
that.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving BIP148
a sense of safety that may not be valid. Without several more steps,
BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain. (Unless
the segwit2x compromise falls apart before then, and even in that case
it is likely to be a minority chain)
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice) however there may be lag time immediately after the
split if there is an economic majority but not a hashpower majority
initially. This is risk mitigation that only requires miners support
however. The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to provide a
risk mitigation measure that miners can safely deploy. Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split. At this point it is not completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until BIP148
activation. I intentionally used a shorter activation period here so
that decisions by miners can be made close to the BIP148 activation
date.
I think this BIP represents a gamble, and the gamble may not be a good
one. The gamble here is that if the segwit2x changes are rolled out
on time, and if the signatories accept the bit4 + bit1 signaling
proposals within BIP91, the launch will go smoother, as intended. But
conversely, if either the segwit2x signatories balk about the Bit1
signaling OR if the timelines for segwit2mb are missed even by a bit,
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble to be
making.
The reason I say it may make the chainsplit be worse than it would
otherwise be is that it may provide a false sense of safety for BIP148
that currently does not currently exist(and should not, as it is a
chainsplit). That sense of safety would only be legitimate if the
segwit2x signatories were on board, and the segwit2x code effectively
enforced BIP148 simultaneously, neither of which are guaranteed. If
users and more miners had a false sense that BIP148 was *not* going to
chainsplit from default / segwit2x, they might not follow the news if
suddenly the segwit2x plan were delayed for a few days. While any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal would
take BIP148 from the "unlikely to have any viable chain after flag day
without segwit2x" category into the "small but viable minority chain"
category, and even worse, it might strengthen the chainsplit just days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the client,
and if BIP148 support were much much broader, I would feel differently
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it (by
strengthening an extreme minority chainsplit that may wind up on the
wrong side of two segwit-activated chains). As it stands now, this
seems like a very dangerous attempt to compromise with a small but
vocal group that are the ones creating the threat to begin with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Jared Lee Richardson via bitcoin-dev
2017-06-07 22:53:14 UTC
Permalink
Raw Message
Post by James Hilliard via bitcoin-dev
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice)

That's not a comparable example. ETC did not face potentially years of
slow blocktimes before it normalized, whereas BIP148 is on track to do
exactly that. Moreover, ETC represented a fundamental break from the
majority consensus that could not be rectified, whereas BIP148 represents
only a minority attempt to accelerate something that an overwhelming
majority of miners have already agreed to activate under segwit2x. Lastly
ETC was required to add replay protection, just like any minority fork
proposed by any crypto-currency has been, something that BIP148 both lacks
and refuses to add or even acknowledge the necessity of. Without replay
protection, ETC could not have become profitable enough to be a viable
minority chain. If BIP148's chain is not the majority chain and it does
not have replay protection, it will face the same problems, but that
required replay protection will turn it into a hardfork. This will be a
very bad position for UASF supporters to find themselves in - Either
hardfork and hope the price is higher and the majority converts, or die as
the minority chain with no reliable methods of economic conversion.

I believe, but don't have data to back this, that most of the BIP148
insistence comes not from a legitimate attempt to gain consensus (or else
they would either outright oppose segwit2mb for its hardfork, or they would
outright support it), but rather from an attempt for BIP148 supporters to
save face for BIP148 being a failure. If I'm correct, that's a terrible
and highly non-technical reason for segwit2mb to bend over backwards
attempting to support BIP148's attempt to save face.
Post by James Hilliard via bitcoin-dev
The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.

Even if I'm not correct on the above, I and others find it hard to accept
that this timeline conflict is segwit2x's fault. Segwit2x has both some
flexibility and broad support that crosses contentious pro-segwit and
pro-blocksize-increase divisions that have existed for two years. BIP148
is attempting to hold segwit2x's timelines and code hostage by claiming
inflexibility and claiming broad support, and not only are neither of those
assertions are backed by real data, BIP148 (by being so inflexible) is
pushing a position that deepens the divides between those groups. For
there to be technical reasons for compatibility (so long as there are
tradeoffs, which there are), there needs to be hard data showing that
BIP148 is a viable minority fork that won't simply die off on its own.

Jared
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?
It's fairly trivial for miners to signal for BIP91 on bit4 or a
different bit at the same time as the code is trivial enough to
combine
Post by Jared Lee Richardson via bitcoin-dev
The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a more
standard approach to activation that requires stronger consensus and
may be more forgiving than BIP148. If the segwit2x activation is on
time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on that
idea? It may add more complexity and more developer time, but may
also address your concerns among others.
This does give miners another approach to activate segwit ahead of
BIP148, if segwit2x activation is rolled out and activated immediately
then this would not be needed however based on the timeline here
https://segwit2x.github.io/ it would not be possible for BIP91 to
enforce mandatory signalling ahead of BIP148. Maybe that can be
changed though, I've suggested an immediate rollout with a placeholder
client timeout instead of the HF code initially in order to accelerate
that.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving BIP148
a sense of safety that may not be valid. Without several more steps,
BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain. (Unless
the segwit2x compromise falls apart before then, and even in that case
it is likely to be a minority chain)
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice) however there may be lag time immediately after the
split if there is an economic majority but not a hashpower majority
initially. This is risk mitigation that only requires miners support
however. The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to provide a
risk mitigation measure that miners can safely deploy. Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split. At this point it is not completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until BIP148
activation. I intentionally used a shorter activation period here so
that decisions by miners can be made close to the BIP148 activation
date.
On Wed, Jun 7, 2017 at 4:29 PM, Jared Lee Richardson <
I think this BIP represents a gamble, and the gamble may not be a good
one. The gamble here is that if the segwit2x changes are rolled out
on time, and if the signatories accept the bit4 + bit1 signaling
proposals within BIP91, the launch will go smoother, as intended. But
conversely, if either the segwit2x signatories balk about the Bit1
signaling OR if the timelines for segwit2mb are missed even by a bit,
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble to be
making.
The reason I say it may make the chainsplit be worse than it would
otherwise be is that it may provide a false sense of safety for BIP148
that currently does not currently exist(and should not, as it is a
chainsplit). That sense of safety would only be legitimate if the
segwit2x signatories were on board, and the segwit2x code effectively
enforced BIP148 simultaneously, neither of which are guaranteed. If
users and more miners had a false sense that BIP148 was *not* going to
chainsplit from default / segwit2x, they might not follow the news if
suddenly the segwit2x plan were delayed for a few days. While any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal would
take BIP148 from the "unlikely to have any viable chain after flag day
without segwit2x" category into the "small but viable minority chain"
category, and even worse, it might strengthen the chainsplit just days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the client,
and if BIP148 support were much much broader, I would feel differently
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it (by
strengthening an extreme minority chainsplit that may wind up on the
wrong side of two segwit-activated chains). As it stands now, this
seems like a very dangerous attempt to compromise with a small but
vocal group that are the ones creating the threat to begin with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) )
//
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00
UTC
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00
UTC
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus())
&&
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...
jameshilliard:splitprotection-v0.14.1
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/
bitcoin-dev/2017-March/013714.html
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.
cpp#L1281-L1283
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit
deployment]]
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
benefits]
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-07 23:11:00 UTC
Permalink
Raw Message
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice)
That's not a comparable example. ETC did not face potentially years of slow
blocktimes before it normalized, whereas BIP148 is on track to do exactly
that. Moreover, ETC represented a fundamental break from the majority
consensus that could not be rectified, whereas BIP148 represents only a
minority attempt to accelerate something that an overwhelming majority of
miners have already agreed to activate under segwit2x. Lastly ETC was
required to add replay protection, just like any minority fork proposed by
any crypto-currency has been, something that BIP148 both lacks and refuses
to add or even acknowledge the necessity of. Without replay protection, ETC
could not have become profitable enough to be a viable minority chain. If
BIP148's chain is not the majority chain and it does not have replay
protection, it will face the same problems, but that required replay
protection will turn it into a hardfork. This will be a very bad position
for UASF supporters to find themselves in - Either hardfork and hope the
price is higher and the majority converts, or die as the minority chain with
no reliable methods of economic conversion.
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction. BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there. ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
Post by James Hilliard via bitcoin-dev
I believe, but don't have data to back this, that most of the BIP148
insistence comes not from a legitimate attempt to gain consensus (or else
they would either outright oppose segwit2mb for its hardfork, or they would
outright support it), but rather from an attempt for BIP148 supporters to
save face for BIP148 being a failure. If I'm correct, that's a terrible and
highly non-technical reason for segwit2mb to bend over backwards attempting
to support BIP148's attempt to save face.
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Even if I'm not correct on the above, I and others find it hard to accept
that this timeline conflict is segwit2x's fault. Segwit2x has both some
flexibility and broad support that crosses contentious pro-segwit and
pro-blocksize-increase divisions that have existed for two years. BIP148 is
attempting to hold segwit2x's timelines and code hostage by claiming
inflexibility and claiming broad support, and not only are neither of those
assertions are backed by real data, BIP148 (by being so inflexible) is
pushing a position that deepens the divides between those groups. For there
to be technical reasons for compatibility (so long as there are tradeoffs,
which there are), there needs to be hard data showing that BIP148 is a
viable minority fork that won't simply die off on its own.
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation, this is especially a problem since it takes a good
deal of time to properly code and test a HF. Unfortunately segwit2x
has been quite inflexible in regards to the bundling aspect even
though there are clearly no technical reasons for it to be there.
Post by James Hilliard via bitcoin-dev
Jared
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?
It's fairly trivial for miners to signal for BIP91 on bit4 or a
different bit at the same time as the code is trivial enough to
combine
Post by Jared Lee Richardson via bitcoin-dev
The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a more
standard approach to activation that requires stronger consensus and
may be more forgiving than BIP148. If the segwit2x activation is on
time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on that
idea? It may add more complexity and more developer time, but may
also address your concerns among others.
This does give miners another approach to activate segwit ahead of
BIP148, if segwit2x activation is rolled out and activated immediately
then this would not be needed however based on the timeline here
https://segwit2x.github.io/ it would not be possible for BIP91 to
enforce mandatory signalling ahead of BIP148. Maybe that can be
changed though, I've suggested an immediate rollout with a placeholder
client timeout instead of the HF code initially in order to accelerate
that.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving BIP148
a sense of safety that may not be valid. Without several more steps,
BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain. (Unless
the segwit2x compromise falls apart before then, and even in that case
it is likely to be a minority chain)
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice) however there may be lag time immediately after the
split if there is an economic majority but not a hashpower majority
initially. This is risk mitigation that only requires miners support
however. The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to provide a
risk mitigation measure that miners can safely deploy. Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split. At this point it is not completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until BIP148
activation. I intentionally used a shorter activation period here so
that decisions by miners can be made close to the BIP148 activation
date.
On Wed, Jun 7, 2017 at 4:29 PM, Jared Lee Richardson
I think this BIP represents a gamble, and the gamble may not be a good
one. The gamble here is that if the segwit2x changes are rolled out
on time, and if the signatories accept the bit4 + bit1 signaling
proposals within BIP91, the launch will go smoother, as intended. But
conversely, if either the segwit2x signatories balk about the Bit1
signaling OR if the timelines for segwit2mb are missed even by a bit,
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble to be
making.
The reason I say it may make the chainsplit be worse than it would
otherwise be is that it may provide a false sense of safety for BIP148
that currently does not currently exist(and should not, as it is a
chainsplit). That sense of safety would only be legitimate if the
segwit2x signatories were on board, and the segwit2x code effectively
enforced BIP148 simultaneously, neither of which are guaranteed. If
users and more miners had a false sense that BIP148 was *not* going to
chainsplit from default / segwit2x, they might not follow the news if
suddenly the segwit2x plan were delayed for a few days. While any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal would
take BIP148 from the "unlikely to have any viable chain after flag day
without segwit2x" category into the "small but viable minority chain"
category, and even worse, it might strengthen the chainsplit just days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the client,
and if BIP148 support were much much broader, I would feel differently
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it (by
strengthening an extreme minority chainsplit that may wind up on the
wrong side of two segwit-activated chains). As it stands now, this
seems like a very dangerous attempt to compromise with a small but
vocal group that are the ones creating the threat to begin with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00 UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00 UTC
(!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Jared Lee Richardson via bitcoin-dev
2017-06-07 23:43:57 UTC
Permalink
Raw Message
Post by James Hilliard via bitcoin-dev
BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there.
This statement is misleading. Wipeout risks don't apply to any consensus
changes; It is a consensus change, it can only be abandoned. The BIP148
chain carries just as many risks of being abandoned or even more with
segwit2x on the table. No miner would consider "wipeout risk" an advantage
when the real threat is chain abandonment.
Post by James Hilliard via bitcoin-dev
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction.
Higher transaction fees suffers the same problem as exchange support does.
Without replay protection, it is very difficult for any average user to
force transactions onto one chain or the other. Thus, without replay
protection, the UASF chain is unlikely to develop any viable fee market;
Its few miners 99% of the time will simply choose from the highest fees
that were already available to the other chain, which is basically no
advantage at all.
Post by James Hilliard via bitcoin-dev
ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
ETC replay protection was added because they were already a hardfork and
without it they would not have had a viable chain. BIP148 is not supposed
to be a hardfork, and if it added replay protection to remain viable it
would lose the frequently touted "wipeout advantage" as well as the ability
to call itself a softfork. And are you seriously suggesting that what
happened with ETC and ETH is a desirable and good situation for Bitcoin,
and that UASF is ETC?
Post by James Hilliard via bitcoin-dev
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
For a miners blowing through six million dollars a day in mining
operational costs, that's a pretty crappy reason. Serious miners can't
afford to prop up a non-viable chain based on philosophy or maybes. BIP148
is based entirely upon people who aren't putting anything on the line
trying to convince others to take the huge risks for them. With
deceptively fallacious logic, in my opinion.

Even segwit2x is based on the assumption that all miners can reach
consensus. Break that assumption and segwit2x will have the same problems
as UASF.
Post by James Hilliard via bitcoin-dev
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation
They are bundled. Segwit alone doesn't have the desired overwhelming
consensus, unless core wishes to fork 71% to 29%, and maybe not even that
high. That's the technical reason, and they can't be unbundled without
breaking that consensus.

Jared
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice)
That's not a comparable example. ETC did not face potentially years of
slow
Post by James Hilliard via bitcoin-dev
blocktimes before it normalized, whereas BIP148 is on track to do exactly
that. Moreover, ETC represented a fundamental break from the majority
consensus that could not be rectified, whereas BIP148 represents only a
minority attempt to accelerate something that an overwhelming majority of
miners have already agreed to activate under segwit2x. Lastly ETC was
required to add replay protection, just like any minority fork proposed
by
Post by James Hilliard via bitcoin-dev
any crypto-currency has been, something that BIP148 both lacks and
refuses
Post by James Hilliard via bitcoin-dev
to add or even acknowledge the necessity of. Without replay protection,
ETC
Post by James Hilliard via bitcoin-dev
could not have become profitable enough to be a viable minority chain.
If
Post by James Hilliard via bitcoin-dev
BIP148's chain is not the majority chain and it does not have replay
protection, it will face the same problems, but that required replay
protection will turn it into a hardfork. This will be a very bad
position
Post by James Hilliard via bitcoin-dev
for UASF supporters to find themselves in - Either hardfork and hope the
price is higher and the majority converts, or die as the minority chain
with
Post by James Hilliard via bitcoin-dev
no reliable methods of economic conversion.
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction. BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there. ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
Post by James Hilliard via bitcoin-dev
I believe, but don't have data to back this, that most of the BIP148
insistence comes not from a legitimate attempt to gain consensus (or else
they would either outright oppose segwit2mb for its hardfork, or they
would
Post by James Hilliard via bitcoin-dev
outright support it), but rather from an attempt for BIP148 supporters to
save face for BIP148 being a failure. If I'm correct, that's a terrible
and
Post by James Hilliard via bitcoin-dev
highly non-technical reason for segwit2mb to bend over backwards
attempting
Post by James Hilliard via bitcoin-dev
to support BIP148's attempt to save face.
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Even if I'm not correct on the above, I and others find it hard to accept
that this timeline conflict is segwit2x's fault. Segwit2x has both some
flexibility and broad support that crosses contentious pro-segwit and
pro-blocksize-increase divisions that have existed for two years.
BIP148 is
Post by James Hilliard via bitcoin-dev
attempting to hold segwit2x's timelines and code hostage by claiming
inflexibility and claiming broad support, and not only are neither of
those
Post by James Hilliard via bitcoin-dev
assertions are backed by real data, BIP148 (by being so inflexible) is
pushing a position that deepens the divides between those groups. For
there
Post by James Hilliard via bitcoin-dev
to be technical reasons for compatibility (so long as there are
tradeoffs,
Post by James Hilliard via bitcoin-dev
which there are), there needs to be hard data showing that BIP148 is a
viable minority fork that won't simply die off on its own.
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation, this is especially a problem since it takes a good
deal of time to properly code and test a HF. Unfortunately segwit2x
has been quite inflexible in regards to the bundling aspect even
though there are clearly no technical reasons for it to be there.
Post by James Hilliard via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 3:23 PM, James Hilliard <
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 4:50 PM, Jared Lee Richardson <
Post by Jared Lee Richardson via bitcoin-dev
Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?
It's fairly trivial for miners to signal for BIP91 on bit4 or a
different bit at the same time as the code is trivial enough to
combine
Post by Jared Lee Richardson via bitcoin-dev
The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a more
standard approach to activation that requires stronger consensus and
may be more forgiving than BIP148. If the segwit2x activation is on
time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on that
idea? It may add more complexity and more developer time, but may
also address your concerns among others.
This does give miners another approach to activate segwit ahead of
BIP148, if segwit2x activation is rolled out and activated immediately
then this would not be needed however based on the timeline here
https://segwit2x.github.io/ it would not be possible for BIP91 to
enforce mandatory signalling ahead of BIP148. Maybe that can be
changed though, I've suggested an immediate rollout with a placeholder
client timeout instead of the HF code initially in order to accelerate
that.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving BIP148
a sense of safety that may not be valid. Without several more steps,
BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain. (Unless
the segwit2x compromise falls apart before then, and even in that case
it is likely to be a minority chain)
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice) however there may be lag time immediately after the
split if there is an economic majority but not a hashpower majority
initially. This is risk mitigation that only requires miners support
however. The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to provide a
risk mitigation measure that miners can safely deploy. Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split. At this point it is not completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until
BIP148
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
activation. I intentionally used a shorter activation period here so
that decisions by miners can be made close to the BIP148 activation
date.
On Wed, Jun 7, 2017 at 4:29 PM, Jared Lee Richardson
I think this BIP represents a gamble, and the gamble may not be a
good
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
one. The gamble here is that if the segwit2x changes are rolled out
on time, and if the signatories accept the bit4 + bit1 signaling
proposals within BIP91, the launch will go smoother, as intended.
But
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
conversely, if either the segwit2x signatories balk about the Bit1
signaling OR if the timelines for segwit2mb are missed even by a
bit,
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places
about
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble to be
making.
The reason I say it may make the chainsplit be worse than it would
otherwise be is that it may provide a false sense of safety for
BIP148
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
that currently does not currently exist(and should not, as it is a
chainsplit). That sense of safety would only be legitimate if the
segwit2x signatories were on board, and the segwit2x code
effectively
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
enforced BIP148 simultaneously, neither of which are guaranteed. If
users and more miners had a false sense that BIP148 was *not* going
to
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
chainsplit from default / segwit2x, they might not follow the news
if
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
suddenly the segwit2x plan were delayed for a few days. While any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal would
take BIP148 from the "unlikely to have any viable chain after flag
day
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
without segwit2x" category into the "small but viable minority
chain"
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
category, and even worse, it might strengthen the chainsplit just
days
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the client,
and if BIP148 support were much much broader, I would feel
differently
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it (by
strengthening an extreme minority chainsplit that may wind up on the
wrong side of two segwit-activated chains). As it stands now, this
seems like a very dangerous attempt to compromise with a small but
vocal group that are the ones creating the threat to begin with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the
Aug
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners
to
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly
ahead
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to
coordinate
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention
to
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header
top
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus()) &&
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())
)
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
//
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK)
==
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block
must
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017
00:00:00
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017
00:00:00
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
UTC
(!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())) )
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK)
==
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block
must
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...
jameshilliard:splitprotection-v0.14.1
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only
if
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for
miners
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
once activated, this ensures that miners are aware of new rules
being
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being
deployed
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we
approach
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/
bitcoin-dev/2017-March/013714.html
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.
cpp#L1281-L1283
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second
deployment)]]
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative
Commons
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-08 00:01:19 UTC
Permalink
Raw Message
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there.
This statement is misleading. Wipeout risks don't apply to any consensus
changes; It is a consensus change, it can only be abandoned. The BIP148
chain carries just as many risks of being abandoned or even more with
segwit2x on the table. No miner would consider "wipeout risk" an advantage
when the real threat is chain abandonment.
Both are issues, but wipeout risk is different, the ETH/ETC split for
example didn't have any wipeout risk for either side the same is not
true for BIP148(and it is the non-BIP148 side that carries the risk of
chain wipeout).
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction.
Higher transaction fees suffers the same problem as exchange support does.
Without replay protection, it is very difficult for any average user to
force transactions onto one chain or the other. Thus, without replay
protection, the UASF chain is unlikely to develop any viable fee market; Its
few miners 99% of the time will simply choose from the highest fees that
were already available to the other chain, which is basically no advantage
at all.
Not really, there are a few relatively simple techniques such as RBF
which can be leveraged to get confirmations on on-side before double
spending on another. Once a transaction is confirmed on the non-BIP148
chain then the high fee transactions can be made on only the BIP148
side of the split using RBF. Exchanges will likely do this splitting
automatically for uses as well.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
ETC replay protection was added because they were already a hardfork and
without it they would not have had a viable chain. BIP148 is not supposed
to be a hardfork, and if it added replay protection to remain viable it
would lose the frequently touted "wipeout advantage" as well as the ability
to call itself a softfork. And are you seriously suggesting that what
happened with ETC and ETH is a desirable and good situation for Bitcoin, and
that UASF is ETC?
There wasn't proper replay protection at split time for ETH/ETC since
normal transactions would get executed on both sides originally,
however replay protection was added by wallets(mainly using splitting
contracts). I don't think a split is desirable however, which is why
I've proposed this BIP.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
For a miners blowing through six million dollars a day in mining operational
costs, that's a pretty crappy reason. Serious miners can't afford to prop
up a non-viable chain based on philosophy or maybes. BIP148 is based
entirely upon people who aren't putting anything on the line trying to
convince others to take the huge risks for them. With deceptively
fallacious logic, in my opinion.
Yes, miners aren't likely to waste operational mining costs, that's
ultimately why miners would follow the BIP148 side of the chain
assuming it has sufficient economic support or if it's more profitable
to mine.
Post by Jared Lee Richardson via bitcoin-dev
Even segwit2x is based on the assumption that all miners can reach
consensus. Break that assumption and segwit2x will have the same problems
as UASF.
segwit2x has more issues since the HF part requires users to reach consensus
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation
They are bundled. Segwit alone doesn't have the desired overwhelming
consensus, unless core wishes to fork 71% to 29%, and maybe not even that
high. That's the technical reason, and they can't be unbundled without
breaking that consensus.
That's a political reason not a technical reason.
Post by Jared Lee Richardson via bitcoin-dev
Jared
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice)
That's not a comparable example. ETC did not face potentially years of slow
blocktimes before it normalized, whereas BIP148 is on track to do exactly
that. Moreover, ETC represented a fundamental break from the majority
consensus that could not be rectified, whereas BIP148 represents only a
minority attempt to accelerate something that an overwhelming majority of
miners have already agreed to activate under segwit2x. Lastly ETC was
required to add replay protection, just like any minority fork proposed by
any crypto-currency has been, something that BIP148 both lacks and refuses
to add or even acknowledge the necessity of. Without replay protection, ETC
could not have become profitable enough to be a viable minority chain.
If
BIP148's chain is not the majority chain and it does not have replay
protection, it will face the same problems, but that required replay
protection will turn it into a hardfork. This will be a very bad position
for UASF supporters to find themselves in - Either hardfork and hope the
price is higher and the majority converts, or die as the minority chain with
no reliable methods of economic conversion.
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction. BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there. ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
Post by James Hilliard via bitcoin-dev
I believe, but don't have data to back this, that most of the BIP148
insistence comes not from a legitimate attempt to gain consensus (or else
they would either outright oppose segwit2mb for its hardfork, or they would
outright support it), but rather from an attempt for BIP148 supporters to
save face for BIP148 being a failure. If I'm correct, that's a terrible and
highly non-technical reason for segwit2mb to bend over backwards attempting
to support BIP148's attempt to save face.
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Even if I'm not correct on the above, I and others find it hard to accept
that this timeline conflict is segwit2x's fault. Segwit2x has both some
flexibility and broad support that crosses contentious pro-segwit and
pro-blocksize-increase divisions that have existed for two years.
BIP148 is
attempting to hold segwit2x's timelines and code hostage by claiming
inflexibility and claiming broad support, and not only are neither of those
assertions are backed by real data, BIP148 (by being so inflexible) is
pushing a position that deepens the divides between those groups. For there
to be technical reasons for compatibility (so long as there are tradeoffs,
which there are), there needs to be hard data showing that BIP148 is a
viable minority fork that won't simply die off on its own.
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation, this is especially a problem since it takes a good
deal of time to properly code and test a HF. Unfortunately segwit2x
has been quite inflexible in regards to the bundling aspect even
though there are clearly no technical reasons for it to be there.
Post by James Hilliard via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 3:23 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 4:50 PM, Jared Lee Richardson
Post by Jared Lee Richardson via bitcoin-dev
Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?
It's fairly trivial for miners to signal for BIP91 on bit4 or a
different bit at the same time as the code is trivial enough to
combine
Post by Jared Lee Richardson via bitcoin-dev
The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a more
standard approach to activation that requires stronger consensus and
may be more forgiving than BIP148. If the segwit2x activation is on
time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on that
idea? It may add more complexity and more developer time, but may
also address your concerns among others.
This does give miners another approach to activate segwit ahead of
BIP148, if segwit2x activation is rolled out and activated immediately
then this would not be needed however based on the timeline here
https://segwit2x.github.io/ it would not be possible for BIP91 to
enforce mandatory signalling ahead of BIP148. Maybe that can be
changed though, I've suggested an immediate rollout with a placeholder
client timeout instead of the HF code initially in order to accelerate
that.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving BIP148
a sense of safety that may not be valid. Without several more steps,
BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain. (Unless
the segwit2x compromise falls apart before then, and even in that case
it is likely to be a minority chain)
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice) however there may be lag time immediately after the
split if there is an economic majority but not a hashpower majority
initially. This is risk mitigation that only requires miners support
however. The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to provide a
risk mitigation measure that miners can safely deploy. Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split. At this point it is not completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until BIP148
activation. I intentionally used a shorter activation period here so
that decisions by miners can be made close to the BIP148 activation
date.
On Wed, Jun 7, 2017 at 4:29 PM, Jared Lee Richardson
I think this BIP represents a gamble, and the gamble may not be a good
one. The gamble here is that if the segwit2x changes are rolled out
on time, and if the signatories accept the bit4 + bit1 signaling
proposals within BIP91, the launch will go smoother, as intended.
But
conversely, if either the segwit2x signatories balk about the Bit1
signaling OR if the timelines for segwit2mb are missed even by a bit,
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble to be
making.
The reason I say it may make the chainsplit be worse than it would
otherwise be is that it may provide a false sense of safety for BIP148
that currently does not currently exist(and should not, as it is a
chainsplit). That sense of safety would only be legitimate if the
segwit2x signatories were on board, and the segwit2x code effectively
enforced BIP148 simultaneously, neither of which are guaranteed.
If
users and more miners had a false sense that BIP148 was *not* going to
chainsplit from default / segwit2x, they might not follow the news if
suddenly the segwit2x plan were delayed for a few days. While any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal would
take BIP148 from the "unlikely to have any viable chain after flag day
without segwit2x" category into the "small but viable minority chain"
category, and even worse, it might strengthen the chainsplit just days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the client,
and if BIP148 support were much much broader, I would feel differently
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it (by
strengthening an extreme minority chainsplit that may wind up on the
wrong side of two segwit-activated chains). As it stands now, this
seems like a very dangerous attempt to compromise with a small but
vocal group that are the ones creating the threat to begin with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use
splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date. Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has reached its
own signalling threshold. This BIP will cease to be active when segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) )
//
and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00
UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00
UTC
(!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners to have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
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Jared Lee Richardson via bitcoin-dev
2017-06-08 00:20:23 UTC
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Post by James Hilliard via bitcoin-dev
Not really, there are a few relatively simple techniques such as RBF
which can be leveraged to get confirmations on on-side before double
spending on another. Once a transaction is confirmed on the non-BIP148
chain then the high fee transactions can be made on only the BIP148
side of the split using RBF.
Ah, so the BIP148 client handles this on behalf of its less technical users
on their behalf then, yes?
Post by James Hilliard via bitcoin-dev
Exchanges will likely do this splitting
automatically for uses as well.
Sure, Exchanges are going to dedicate hundreds of developer hours and
thousands of support hours to support something that they've repeatedly
told everyone must have replay protection to be supported. They're going
to do this because 8% of nodes and <0.5% of miners say they'll be rewarded
richly. Somehow I find that hard to believe.

Besides, if the BIP148 client does it for them, they wouldn't have to
dedicate those hundreds of developer hours. Right?

I can't imagine how this logic is getting you from where the real data is
to the assumption that an economic majority will push BIP148 into being
such a more valuable chain that switching chains will be attractive to
enough miners. There's got to be some real data that convinces you of this
somewhere?
Post by James Hilliard via bitcoin-dev
Both are issues, but wipeout risk is different, the ETH/ETC split for
example didn't have any wipeout risk for either side the same is not
true for BIP148(and it is the non-BIP148 side that carries the risk of
chain wipeout).
Wipeout risk is a serious issue when 45% of the miners support one chain
and 55% support the other chain. Segwit doesn't even have 35% of the
miners; There's no data or statements anywhere that indicate that UASF is
going to reach the point where wipeout risk is even comparable to
abandonment risk.
Post by James Hilliard via bitcoin-dev
Yes, miners aren't likely to waste operational mining costs, that's
ultimately why miners would follow the BIP148 side of the chain
assuming it has sufficient economic support or if it's more profitable
to mine.
To convince miners you would have to have some data SOMEWHERE supporting
the economic majority argument. Is there any such data?
Post by James Hilliard via bitcoin-dev
segwit2x has more issues since the HF part requires users to reach consensus
It doesn't have those issues during the segwit activation, ergo there is no
reason for segwit-activation problems to take priority over the very real
hardfork activation problems.
Post by James Hilliard via bitcoin-dev
That's a political reason not a technical reason.
In a consensus system they are frequently the same, unfortunately.
Technical awesomeness without people agreeing = zero consensus. So the
choice is either to "technically" break the consensus without a
super-majority and see what happens, or to go with the choice that has real
data showing the most consensus and hope the tiny minority chain actually
dies off.

Jared
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there.
This statement is misleading. Wipeout risks don't apply to any consensus
changes; It is a consensus change, it can only be abandoned. The BIP148
chain carries just as many risks of being abandoned or even more with
segwit2x on the table. No miner would consider "wipeout risk" an
advantage
Post by Jared Lee Richardson via bitcoin-dev
when the real threat is chain abandonment.
Both are issues, but wipeout risk is different, the ETH/ETC split for
example didn't have any wipeout risk for either side the same is not
true for BIP148(and it is the non-BIP148 side that carries the risk of
chain wipeout).
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction.
Higher transaction fees suffers the same problem as exchange support
does.
Post by Jared Lee Richardson via bitcoin-dev
Without replay protection, it is very difficult for any average user to
force transactions onto one chain or the other. Thus, without replay
protection, the UASF chain is unlikely to develop any viable fee market;
Its
Post by Jared Lee Richardson via bitcoin-dev
few miners 99% of the time will simply choose from the highest fees that
were already available to the other chain, which is basically no
advantage
Post by Jared Lee Richardson via bitcoin-dev
at all.
Not really, there are a few relatively simple techniques such as RBF
which can be leveraged to get confirmations on on-side before double
spending on another. Once a transaction is confirmed on the non-BIP148
chain then the high fee transactions can be made on only the BIP148
side of the split using RBF. Exchanges will likely do this splitting
automatically for uses as well.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
ETC replay protection was added because they were already a hardfork and
without it they would not have had a viable chain. BIP148 is not
supposed
Post by Jared Lee Richardson via bitcoin-dev
to be a hardfork, and if it added replay protection to remain viable it
would lose the frequently touted "wipeout advantage" as well as the
ability
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to call itself a softfork. And are you seriously suggesting that what
happened with ETC and ETH is a desirable and good situation for Bitcoin,
and
Post by Jared Lee Richardson via bitcoin-dev
that UASF is ETC?
There wasn't proper replay protection at split time for ETH/ETC since
normal transactions would get executed on both sides originally,
however replay protection was added by wallets(mainly using splitting
contracts). I don't think a split is desirable however, which is why
I've proposed this BIP.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
For a miners blowing through six million dollars a day in mining
operational
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costs, that's a pretty crappy reason. Serious miners can't afford to
prop
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up a non-viable chain based on philosophy or maybes. BIP148 is based
entirely upon people who aren't putting anything on the line trying to
convince others to take the huge risks for them. With deceptively
fallacious logic, in my opinion.
Yes, miners aren't likely to waste operational mining costs, that's
ultimately why miners would follow the BIP148 side of the chain
assuming it has sufficient economic support or if it's more profitable
to mine.
Post by Jared Lee Richardson via bitcoin-dev
Even segwit2x is based on the assumption that all miners can reach
consensus. Break that assumption and segwit2x will have the same
problems
Post by Jared Lee Richardson via bitcoin-dev
as UASF.
segwit2x has more issues since the HF part requires users to reach consensus
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation
They are bundled. Segwit alone doesn't have the desired overwhelming
consensus, unless core wishes to fork 71% to 29%, and maybe not even that
high. That's the technical reason, and they can't be unbundled without
breaking that consensus.
That's a political reason not a technical reason.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 4:11 PM, James Hilliard <
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 5:53 PM, Jared Lee Richardson <
Post by James Hilliard via bitcoin-dev
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There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice)
That's not a comparable example. ETC did not face potentially years
of
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slow
blocktimes before it normalized, whereas BIP148 is on track to do exactly
that. Moreover, ETC represented a fundamental break from the majority
consensus that could not be rectified, whereas BIP148 represents only
a
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minority attempt to accelerate something that an overwhelming majority of
miners have already agreed to activate under segwit2x. Lastly ETC was
required to add replay protection, just like any minority fork
proposed
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by
any crypto-currency has been, something that BIP148 both lacks and refuses
to add or even acknowledge the necessity of. Without replay
protection,
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ETC
could not have become profitable enough to be a viable minority chain.
If
BIP148's chain is not the majority chain and it does not have replay
protection, it will face the same problems, but that required replay
protection will turn it into a hardfork. This will be a very bad position
for UASF supporters to find themselves in - Either hardfork and hope
the
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price is higher and the majority converts, or die as the minority
chain
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with
no reliable methods of economic conversion.
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction. BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there. ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
Post by James Hilliard via bitcoin-dev
I believe, but don't have data to back this, that most of the BIP148
insistence comes not from a legitimate attempt to gain consensus (or else
they would either outright oppose segwit2mb for its hardfork, or they would
outright support it), but rather from an attempt for BIP148 supporters to
save face for BIP148 being a failure. If I'm correct, that's a
terrible
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and
highly non-technical reason for segwit2mb to bend over backwards attempting
to support BIP148's attempt to save face.
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
Post by James Hilliard via bitcoin-dev
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The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Even if I'm not correct on the above, I and others find it hard to accept
that this timeline conflict is segwit2x's fault. Segwit2x has both
some
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flexibility and broad support that crosses contentious pro-segwit and
pro-blocksize-increase divisions that have existed for two years.
BIP148 is
attempting to hold segwit2x's timelines and code hostage by claiming
inflexibility and claiming broad support, and not only are neither of those
assertions are backed by real data, BIP148 (by being so inflexible) is
pushing a position that deepens the divides between those groups. For there
to be technical reasons for compatibility (so long as there are tradeoffs,
which there are), there needs to be hard data showing that BIP148 is a
viable minority fork that won't simply die off on its own.
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation, this is especially a problem since it takes a good
deal of time to properly code and test a HF. Unfortunately segwit2x
has been quite inflexible in regards to the bundling aspect even
though there are clearly no technical reasons for it to be there.
Post by James Hilliard via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 3:23 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 4:50 PM, Jared Lee Richardson
Post by Jared Lee Richardson via bitcoin-dev
Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?
It's fairly trivial for miners to signal for BIP91 on bit4 or a
different bit at the same time as the code is trivial enough to
combine
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The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a
more
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standard approach to activation that requires stronger consensus
and
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may be more forgiving than BIP148. If the segwit2x activation is
on
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time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on
that
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idea? It may add more complexity and more developer time, but may
also address your concerns among others.
This does give miners another approach to activate segwit ahead of
BIP148, if segwit2x activation is rolled out and activated
immediately
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then this would not be needed however based on the timeline here
https://segwit2x.github.io/ it would not be possible for BIP91 to
enforce mandatory signalling ahead of BIP148. Maybe that can be
changed though, I've suggested an immediate rollout with a
placeholder
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client timeout instead of the HF code initially in order to
accelerate
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that.
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Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving
BIP148
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a sense of safety that may not be valid. Without several more
steps,
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BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain.
(Unless
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the segwit2x compromise falls apart before then, and even in that case
it is likely to be a minority chain)
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how
this
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works in practice) however there may be lag time immediately after
the
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split if there is an economic majority but not a hashpower majority
initially. This is risk mitigation that only requires miners support
however. The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to
provide
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a
risk mitigation measure that miners can safely deploy. Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split. At this point it is not
completely
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clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until BIP148
activation. I intentionally used a shorter activation period here
so
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that decisions by miners can be made close to the BIP148
activation
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date.
On Wed, Jun 7, 2017 at 4:29 PM, Jared Lee Richardson
I think this BIP represents a gamble, and the gamble may not be a good
one. The gamble here is that if the segwit2x changes are rolled out
on time, and if the signatories accept the bit4 + bit1 signaling
proposals within BIP91, the launch will go smoother, as intended.
But
conversely, if either the segwit2x signatories balk about the
Bit1
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signaling OR if the timelines for segwit2mb are missed even by a bit,
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble to be
making.
The reason I say it may make the chainsplit be worse than it
would
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otherwise be is that it may provide a false sense of safety for BIP148
that currently does not currently exist(and should not, as it is
a
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chainsplit). That sense of safety would only be legitimate if
the
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segwit2x signatories were on board, and the segwit2x code effectively
enforced BIP148 simultaneously, neither of which are guaranteed.
If
users and more miners had a false sense that BIP148 was *not*
going
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to
chainsplit from default / segwit2x, they might not follow the
news
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if
suddenly the segwit2x plan were delayed for a few days. While
any
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additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal
would
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take BIP148 from the "unlikely to have any viable chain after
flag
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day
without segwit2x" category into the "small but viable minority chain"
category, and even worse, it might strengthen the chainsplit just days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the client,
and if BIP148 support were much much broader, I would feel differently
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it
(by
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strengthening an extreme minority chainsplit that may wind up on the
wrong side of two segwit-activated chains). As it stands now,
this
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seems like a very dangerous attempt to compromise with a small
but
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vocal group that are the ones creating the threat to begin with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
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Due to the proposed calendar(https://segwit2x.github.io/) for
the
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SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose
another
option that miners can use to prevent a chain split ahead of the Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using
BIP8
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instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of
miners
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to
activate mandatory SegWit signalling and prevent a potential
chain
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split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly ahead
of BIP148 activation by signalling for splitprotection. Any
miners
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already running BIP148 should be encouraged to use
splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple
majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit"
deployment
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using bit 1, between November 15th 2016 and November 15th 2017
to
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activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that
risk.
This BIP provides a way for a simple majority of miners to coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints
unless
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immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date.
Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their
intention
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to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion
header
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top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as
required
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will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can
be
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adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017
(epoch
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time 1501545600) regardless of whether or not this BIP has
reached
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its
own signalling threshold. This BIP will cease to be active when
segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev,
chainparams.GetConsensus(),
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Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
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&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())
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)
//
and is not active.
{
bool fVersionBits = (pindex->nVersion &
VERSIONBITS_TOP_MASK)
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==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017 00:00:00
UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017 00:00:00
UTC
(!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion &
VERSIONBITS_TOP_MASK)
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==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...
jameshilliard:splitprotection-v0.14.1
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==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and
midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91
only
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if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they
may
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build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft
forks
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such as BIP66 which has a mandatory signalling requirement for miners
once activated, this ensures that miners are aware of new rules being
enforced. This technique can be leveraged to lower the
signalling
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threshold of a soft fork while it is in the process of being deployed
in a backwards compatible way. We also use a BIP8 style timeout
to
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ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1
"segwit"
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deployment, this BIP can cause the existing "segwit" deployment
to
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activate without needing to release a new deployment. As we approach
BIP148 activation it may be desirable for a majority of miners
to
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have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/
bitcoin-dev/2017-March/013714.html
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Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.
cpp#L1281-L1283
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P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit
deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
James Hilliard via bitcoin-dev
2017-06-08 00:44:38 UTC
Permalink
Raw Message
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Not really, there are a few relatively simple techniques such as RBF
which can be leveraged to get confirmations on on-side before double
spending on another. Once a transaction is confirmed on the non-BIP148
chain then the high fee transactions can be made on only the BIP148
side of the split using RBF.
Ah, so the BIP148 client handles this on behalf of its less technical users
on their behalf then, yes?
It's not automatic but exchanges will likely handle it on behalf of
the less technical users. BIP148 is not intended to cause a permanent
chain split however which is why this was not built in.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Exchanges will likely do this splitting
automatically for uses as well.
Sure, Exchanges are going to dedicate hundreds of developer hours and
thousands of support hours to support something that they've repeatedly told
everyone must have replay protection to be supported. They're going to do
this because 8% of nodes and <0.5% of miners say they'll be rewarded richly.
Somehow I find that hard to believe.
They are very likely to, most have contingency plans for this sort of
thing ready to go due to their experience with the ETH/ETC fork.
Post by Jared Lee Richardson via bitcoin-dev
Besides, if the BIP148 client does it for them, they wouldn't have to
dedicate those hundreds of developer hours. Right?
I can't imagine how this logic is getting you from where the real data is to
the assumption that an economic majority will push BIP148 into being such a
more valuable chain that switching chains will be attractive to enough
miners. There's got to be some real data that convinces you of this
somewhere?
If you're looking for hard numbers at this point you aren't likely to
find them because not everything is easy to measure directly.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Both are issues, but wipeout risk is different, the ETH/ETC split for
example didn't have any wipeout risk for either side the same is not
true for BIP148(and it is the non-BIP148 side that carries the risk of
chain wipeout).
Wipeout risk is a serious issue when 45% of the miners support one chain and
55% support the other chain. Segwit doesn't even have 35% of the miners;
There's no data or statements anywhere that indicate that UASF is going to
reach the point where wipeout risk is even comparable to abandonment risk.
It's mostly economic support that will dictate this, not hashpower
support since the hashpower follows the economy.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Yes, miners aren't likely to waste operational mining costs, that's
ultimately why miners would follow the BIP148 side of the chain
assuming it has sufficient economic support or if it's more profitable
to mine.
To convince miners you would have to have some data SOMEWHERE supporting the
economic majority argument. Is there any such data?
We'll know more as we get closer to BIP148 activation by looking at the markets.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
segwit2x has more issues since the HF part requires users to reach consensus
It doesn't have those issues during the segwit activation, ergo there is no
reason for segwit-activation problems to take priority over the very real
hardfork activation problems.
And yet segwit2x is insisting on activation bundling which needlessly
complicates and delays SegWit activation.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
That's a political reason not a technical reason.
In a consensus system they are frequently the same, unfortunately.
Technical awesomeness without people agreeing = zero consensus. So the
choice is either to "technically" break the consensus without a
super-majority and see what happens, or to go with the choice that has real
data showing the most consensus and hope the tiny minority chain actually
dies off.
Sure, technical changes can be made for political reasons, we should
at least be clear in regards to why particular decisions are being
made. I'm supportive of a hard fork for technical reasons but not
political ones as are many others.
Post by Jared Lee Richardson via bitcoin-dev
Jared
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BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there.
This statement is misleading. Wipeout risks don't apply to any consensus
changes; It is a consensus change, it can only be abandoned. The BIP148
chain carries just as many risks of being abandoned or even more with
segwit2x on the table. No miner would consider "wipeout risk" an advantage
when the real threat is chain abandonment.
Both are issues, but wipeout risk is different, the ETH/ETC split for
example didn't have any wipeout risk for either side the same is not
true for BIP148(and it is the non-BIP148 side that carries the risk of
chain wipeout).
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction.
Higher transaction fees suffers the same problem as exchange support does.
Without replay protection, it is very difficult for any average user to
force transactions onto one chain or the other. Thus, without replay
protection, the UASF chain is unlikely to develop any viable fee market; Its
few miners 99% of the time will simply choose from the highest fees that
were already available to the other chain, which is basically no advantage
at all.
Not really, there are a few relatively simple techniques such as RBF
which can be leveraged to get confirmations on on-side before double
spending on another. Once a transaction is confirmed on the non-BIP148
chain then the high fee transactions can be made on only the BIP148
side of the split using RBF. Exchanges will likely do this splitting
automatically for uses as well.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
ETC replay protection was added because they were already a hardfork and
without it they would not have had a viable chain. BIP148 is not supposed
to be a hardfork, and if it added replay protection to remain viable it
would lose the frequently touted "wipeout advantage" as well as the ability
to call itself a softfork. And are you seriously suggesting that what
happened with ETC and ETH is a desirable and good situation for Bitcoin, and
that UASF is ETC?
There wasn't proper replay protection at split time for ETH/ETC since
normal transactions would get executed on both sides originally,
however replay protection was added by wallets(mainly using splitting
contracts). I don't think a split is desirable however, which is why
I've proposed this BIP.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
For a miners blowing through six million dollars a day in mining operational
costs, that's a pretty crappy reason. Serious miners can't afford to prop
up a non-viable chain based on philosophy or maybes. BIP148 is based
entirely upon people who aren't putting anything on the line trying to
convince others to take the huge risks for them. With deceptively
fallacious logic, in my opinion.
Yes, miners aren't likely to waste operational mining costs, that's
ultimately why miners would follow the BIP148 side of the chain
assuming it has sufficient economic support or if it's more profitable
to mine.
Post by Jared Lee Richardson via bitcoin-dev
Even segwit2x is based on the assumption that all miners can reach
consensus. Break that assumption and segwit2x will have the same problems
as UASF.
segwit2x has more issues since the HF part requires users to reach consensus
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation
They are bundled. Segwit alone doesn't have the desired overwhelming
consensus, unless core wishes to fork 71% to 29%, and maybe not even that
high. That's the technical reason, and they can't be unbundled without
breaking that consensus.
That's a political reason not a technical reason.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 4:11 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 5:53 PM, Jared Lee Richardson
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice)
That's not a comparable example. ETC did not face potentially years of
slow
blocktimes before it normalized, whereas BIP148 is on track to do exactly
that. Moreover, ETC represented a fundamental break from the majority
consensus that could not be rectified, whereas BIP148 represents only a
minority attempt to accelerate something that an overwhelming
majority
of
miners have already agreed to activate under segwit2x. Lastly ETC was
required to add replay protection, just like any minority fork proposed
by
any crypto-currency has been, something that BIP148 both lacks and refuses
to add or even acknowledge the necessity of. Without replay protection,
ETC
could not have become profitable enough to be a viable minority chain.
If
BIP148's chain is not the majority chain and it does not have replay
protection, it will face the same problems, but that required replay
protection will turn it into a hardfork. This will be a very bad position
for UASF supporters to find themselves in - Either hardfork and hope the
price is higher and the majority converts, or die as the minority chain
with
no reliable methods of economic conversion.
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction. BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there. ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
Post by James Hilliard via bitcoin-dev
I believe, but don't have data to back this, that most of the BIP148
insistence comes not from a legitimate attempt to gain consensus (or else
they would either outright oppose segwit2mb for its hardfork, or they would
outright support it), but rather from an attempt for BIP148
supporters
to
save face for BIP148 being a failure. If I'm correct, that's a terrible
and
highly non-technical reason for segwit2mb to bend over backwards attempting
to support BIP148's attempt to save face.
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Even if I'm not correct on the above, I and others find it hard to accept
that this timeline conflict is segwit2x's fault. Segwit2x has both some
flexibility and broad support that crosses contentious pro-segwit and
pro-blocksize-increase divisions that have existed for two years.
BIP148 is
attempting to hold segwit2x's timelines and code hostage by claiming
inflexibility and claiming broad support, and not only are neither of those
assertions are backed by real data, BIP148 (by being so inflexible) is
pushing a position that deepens the divides between those groups.
For
there
to be technical reasons for compatibility (so long as there are tradeoffs,
which there are), there needs to be hard data showing that BIP148 is a
viable minority fork that won't simply die off on its own.
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation, this is especially a problem since it takes a good
deal of time to properly code and test a HF. Unfortunately segwit2x
has been quite inflexible in regards to the bundling aspect even
though there are clearly no technical reasons for it to be there.
Post by James Hilliard via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 3:23 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 4:50 PM, Jared Lee Richardson
Post by Jared Lee Richardson via bitcoin-dev
Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?
It's fairly trivial for miners to signal for BIP91 on bit4 or a
different bit at the same time as the code is trivial enough to
combine
Post by Jared Lee Richardson via bitcoin-dev
The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a more
standard approach to activation that requires stronger consensus and
may be more forgiving than BIP148. If the segwit2x activation is on
time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on that
idea? It may add more complexity and more developer time, but may
also address your concerns among others.
This does give miners another approach to activate segwit ahead of
BIP148, if segwit2x activation is rolled out and activated immediately
then this would not be needed however based on the timeline here
https://segwit2x.github.io/ it would not be possible for BIP91 to
enforce mandatory signalling ahead of BIP148. Maybe that can be
changed though, I've suggested an immediate rollout with a placeholder
client timeout instead of the HF code initially in order to accelerate
that.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving BIP148
a sense of safety that may not be valid. Without several more steps,
BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain. (Unless
the segwit2x compromise falls apart before then, and even in that case
it is likely to be a minority chain)
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice) however there may be lag time immediately after the
split if there is an economic majority but not a hashpower majority
initially. This is risk mitigation that only requires miners support
however. The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to
provide
a
risk mitigation measure that miners can safely deploy. Since this BIP
only activates with a clear miner majority it should not increase the
risk of an extended chain split. At this point it is not completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until BIP148
activation. I intentionally used a shorter activation period here so
that decisions by miners can be made close to the BIP148 activation
date.
On Wed, Jun 7, 2017 at 4:29 PM, Jared Lee Richardson
I think this BIP represents a gamble, and the gamble may not be a
good
one. The gamble here is that if the segwit2x changes are rolled out
on time, and if the signatories accept the bit4 + bit1 signaling
proposals within BIP91, the launch will go smoother, as intended.
But
conversely, if either the segwit2x signatories balk about the Bit1
signaling OR if the timelines for segwit2mb are missed even by a bit,
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble
to
be
making.
The reason I say it may make the chainsplit be worse than it would
otherwise be is that it may provide a false sense of safety for
BIP148
that currently does not currently exist(and should not, as it is a
chainsplit). That sense of safety would only be legitimate if the
segwit2x signatories were on board, and the segwit2x code effectively
enforced BIP148 simultaneously, neither of which are guaranteed.
If
users and more miners had a false sense that BIP148 was *not* going
to
chainsplit from default / segwit2x, they might not follow the news
if
suddenly the segwit2x plan were delayed for a few days. While any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal would
take BIP148 from the "unlikely to have any viable chain after flag
day
without segwit2x" category into the "small but viable minority chain"
category, and even worse, it might strengthen the chainsplit just
days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the client,
and if BIP148 support were much much broader, I would feel
differently
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it (by
strengthening an extreme minority chainsplit that may wind up on the
wrong side of two segwit-activated chains). As it stands now, this
seems like a very dangerous attempt to compromise with a small but
vocal group that are the ones creating the threat to begin with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for the
SegWit2x agreement being too slow to activate SegWit mandatory
signalling ahead of BIP148 using BIP91 I would like to propose
another
option that miners can use to prevent a chain split ahead of the
Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using BIP8
instead of BIP9 with a lower activation threshold and immediate
mandatory signalling lock-in. This allows for a majority of miners
to
activate mandatory SegWit signalling and prevent a potential chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces quickly
ahead
of BIP148 activation by signalling for splitprotection. Any miners
already running BIP148 should be encouraged to use
splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple
majority
of miners to prevent a chain split ahead of BIP148 activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit" deployment
using bit 1, between November 15th 2016 and November 15th 2017 to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this BIP
provides a way for a simple majority of miners to eliminate that
risk.
This BIP provides a way for a simple majority of miners to
coordinate
activation of the existing segwit deployment with less than 95%
hashpower before BIP148 activation. Due to time constraints unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation of
BIP148. This BIP provides a method for rapid miner activation of
SegWit mandatory signalling ahead of the BIP148 activation date.
Since
the primary goal of this BIP is to reduce the chance of an extended
chain split as much as possible we activate using a simple miner
majority of 65% over a 504 block interval rather than a higher
percentage. This BIP also allows miners to signal their intention
to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion header
top
3 bits to 001 together with bit field (1<<1) (according to the
existing segwit deployment). Blocks that do not signal as required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this can be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork since
mandatory signalling will start on midnight August 1st 2017 (epoch
time 1501545600) regardless of whether or not this BIP has
reached
its
own signalling threshold. This BIP will cease to be active when
segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev,
chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())
)
//
and is not active.
{
bool fVersionBits = (pindex->nVersion &
VERSIONBITS_TOP_MASK)
==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block
must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017
00:00:00
UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017
00:00:00
UTC
(!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion &
VERSIONBITS_TOP_MASK)
==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed block
must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit 1
deployment scheduled between midnight November 15th, 2016 and
midnight
November 15th, 2017. This deployment is also compatible with the
existing BIP148 deployment. This BIP is compatible with BIP91 only
if
BIP91 activates before it and before BIP148. Miners will need to
upgrade their nodes to support splitprotection otherwise they may
build on top of an invalid block. While this bip is active users
should either upgrade to splitprotection or wait for additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft forks
such as BIP66 which has a mandatory signalling requirement for
miners
once activated, this ensures that miners are aware of new rules
being
enforced. This technique can be leveraged to lower the signalling
threshold of a soft fork while it is in the process of being
deployed
in a backwards compatible way. We also use a BIP8 style timeout to
ensure that this BIP is compatible with BIP148 and that BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
deployment, this BIP can cause the existing "segwit" deployment to
activate without needing to release a new deployment. As we
approach
BIP148 activation it may be desirable for a majority of miners
to
have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit
deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second
deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative
Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Jared Lee Richardson via bitcoin-dev
2017-06-08 01:01:38 UTC
Permalink
Raw Message
Post by James Hilliard via bitcoin-dev
If you're looking for hard numbers at this point you aren't likely to
find them because not everything is easy to measure directly.
There's quite a few hard numbers that are available that are of varying
use. Mining commitments are a major one because of the stalled chain
problem. Node signaling represents some data because while it can be
sybiled, they are cheap but not free to run. Upvotes and comments on
reddit and other forums might be of some use, but there's not a clear
supermajority driving every pro-uasf comment up and every anti-uasf comment
down, and Reddit obscures the upvote/downvotes pretty well. It could be a
gleaned datapoint if someone pulled the comments, manually evaluated their
likely position on the matter(neutrally), and then reported on it, but that
is a lot of work and I think it is unlikely to show anything except how
deep the rifts in the community are. Of the two main statistics available,
they do not support the idea that UASF has any chance of success. Of the
third, it at least shows that there is deep opposition that is nearly equal
to the support amongst the forums most likely to support UASF.

So I'll take anything, any statistic that actually indicates UASF has a
chance in hell of succeeding, at least that would be worth something.
Otherwise it's all much ado about nothing.
Post by James Hilliard via bitcoin-dev
We'll know more as we get closer to BIP148 activation by looking at the markets.
What markets? Where? How would we know?
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
It doesn't have those issues during the segwit activation, ergo there is no
reason for segwit-activation problems to take priority over the very real
hardfork activation problems.
And yet segwit2x is insisting on activation bundling which needlessly
complicates and delays SegWit activation.
Because it is not segwit that has appears to have the supermajority
consensus.
Post by James Hilliard via bitcoin-dev
Sure, technical changes can be made for political reasons, we should
at least be clear in regards to why particular decisions are being
made. I'm supportive of a hard fork for technical reasons but not
political ones as are many others.
Well, then we have a point of agreement at least. :)
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Not really, there are a few relatively simple techniques such as RBF
which can be leveraged to get confirmations on on-side before double
spending on another. Once a transaction is confirmed on the non-BIP148
chain then the high fee transactions can be made on only the BIP148
side of the split using RBF.
Ah, so the BIP148 client handles this on behalf of its less technical
users
Post by Jared Lee Richardson via bitcoin-dev
on their behalf then, yes?
It's not automatic but exchanges will likely handle it on behalf of
the less technical users. BIP148 is not intended to cause a permanent
chain split however which is why this was not built in.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Exchanges will likely do this splitting
automatically for uses as well.
Sure, Exchanges are going to dedicate hundreds of developer hours and
thousands of support hours to support something that they've repeatedly
told
Post by Jared Lee Richardson via bitcoin-dev
everyone must have replay protection to be supported. They're going to
do
Post by Jared Lee Richardson via bitcoin-dev
this because 8% of nodes and <0.5% of miners say they'll be rewarded
richly.
Post by Jared Lee Richardson via bitcoin-dev
Somehow I find that hard to believe.
They are very likely to, most have contingency plans for this sort of
thing ready to go due to their experience with the ETH/ETC fork.
Post by Jared Lee Richardson via bitcoin-dev
Besides, if the BIP148 client does it for them, they wouldn't have to
dedicate those hundreds of developer hours. Right?
I can't imagine how this logic is getting you from where the real data
is to
Post by Jared Lee Richardson via bitcoin-dev
the assumption that an economic majority will push BIP148 into being
such a
Post by Jared Lee Richardson via bitcoin-dev
more valuable chain that switching chains will be attractive to enough
miners. There's got to be some real data that convinces you of this
somewhere?
If you're looking for hard numbers at this point you aren't likely to
find them because not everything is easy to measure directly.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Both are issues, but wipeout risk is different, the ETH/ETC split for
example didn't have any wipeout risk for either side the same is not
true for BIP148(and it is the non-BIP148 side that carries the risk of
chain wipeout).
Wipeout risk is a serious issue when 45% of the miners support one chain
and
Post by Jared Lee Richardson via bitcoin-dev
55% support the other chain. Segwit doesn't even have 35% of the miners;
There's no data or statements anywhere that indicate that UASF is going
to
Post by Jared Lee Richardson via bitcoin-dev
reach the point where wipeout risk is even comparable to abandonment
risk.
It's mostly economic support that will dictate this, not hashpower
support since the hashpower follows the economy.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Yes, miners aren't likely to waste operational mining costs, that's
ultimately why miners would follow the BIP148 side of the chain
assuming it has sufficient economic support or if it's more profitable
to mine.
To convince miners you would have to have some data SOMEWHERE supporting
the
Post by Jared Lee Richardson via bitcoin-dev
economic majority argument. Is there any such data?
We'll know more as we get closer to BIP148 activation by looking at the markets.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
segwit2x has more issues since the HF part requires users to reach consensus
It doesn't have those issues during the segwit activation, ergo there is
no
Post by Jared Lee Richardson via bitcoin-dev
reason for segwit-activation problems to take priority over the very real
hardfork activation problems.
And yet segwit2x is insisting on activation bundling which needlessly
complicates and delays SegWit activation.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
That's a political reason not a technical reason.
In a consensus system they are frequently the same, unfortunately.
Technical awesomeness without people agreeing = zero consensus. So the
choice is either to "technically" break the consensus without a
super-majority and see what happens, or to go with the choice that has
real
Post by Jared Lee Richardson via bitcoin-dev
data showing the most consensus and hope the tiny minority chain actually
dies off.
Sure, technical changes can be made for political reasons, we should
at least be clear in regards to why particular decisions are being
made. I'm supportive of a hard fork for technical reasons but not
political ones as are many others.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 5:01 PM, James Hilliard <
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 6:43 PM, Jared Lee Richardson <
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there.
This statement is misleading. Wipeout risks don't apply to any consensus
changes; It is a consensus change, it can only be abandoned. The
BIP148
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
chain carries just as many risks of being abandoned or even more with
segwit2x on the table. No miner would consider "wipeout risk" an advantage
when the real threat is chain abandonment.
Both are issues, but wipeout risk is different, the ETH/ETC split for
example didn't have any wipeout risk for either side the same is not
true for BIP148(and it is the non-BIP148 side that carries the risk of
chain wipeout).
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction.
Higher transaction fees suffers the same problem as exchange support does.
Without replay protection, it is very difficult for any average user
to
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
force transactions onto one chain or the other. Thus, without replay
protection, the UASF chain is unlikely to develop any viable fee
market;
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Its
few miners 99% of the time will simply choose from the highest fees
that
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
were already available to the other chain, which is basically no advantage
at all.
Not really, there are a few relatively simple techniques such as RBF
which can be leveraged to get confirmations on on-side before double
spending on another. Once a transaction is confirmed on the non-BIP148
chain then the high fee transactions can be made on only the BIP148
side of the split using RBF. Exchanges will likely do this splitting
automatically for uses as well.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
ETC replay protection was added because they were already a hardfork
and
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
without it they would not have had a viable chain. BIP148 is not supposed
to be a hardfork, and if it added replay protection to remain viable
it
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
would lose the frequently touted "wipeout advantage" as well as the ability
to call itself a softfork. And are you seriously suggesting that what
happened with ETC and ETH is a desirable and good situation for
Bitcoin,
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
and
that UASF is ETC?
There wasn't proper replay protection at split time for ETH/ETC since
normal transactions would get executed on both sides originally,
however replay protection was added by wallets(mainly using splitting
contracts). I don't think a split is desirable however, which is why
I've proposed this BIP.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
For a miners blowing through six million dollars a day in mining operational
costs, that's a pretty crappy reason. Serious miners can't afford to prop
up a non-viable chain based on philosophy or maybes. BIP148 is based
entirely upon people who aren't putting anything on the line trying to
convince others to take the huge risks for them. With deceptively
fallacious logic, in my opinion.
Yes, miners aren't likely to waste operational mining costs, that's
ultimately why miners would follow the BIP148 side of the chain
assuming it has sufficient economic support or if it's more profitable
to mine.
Post by Jared Lee Richardson via bitcoin-dev
Even segwit2x is based on the assumption that all miners can reach
consensus. Break that assumption and segwit2x will have the same problems
as UASF.
segwit2x has more issues since the HF part requires users to reach consensus
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to
delay
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
BIP91 activation
They are bundled. Segwit alone doesn't have the desired overwhelming
consensus, unless core wishes to fork 71% to 29%, and maybe not even that
high. That's the technical reason, and they can't be unbundled
without
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
breaking that consensus.
That's a political reason not a technical reason.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 4:11 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 5:53 PM, Jared Lee Richardson
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice)
That's not a comparable example. ETC did not face potentially
years
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
of
slow
blocktimes before it normalized, whereas BIP148 is on track to do exactly
that. Moreover, ETC represented a fundamental break from the majority
consensus that could not be rectified, whereas BIP148 represents
only
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
a
minority attempt to accelerate something that an overwhelming
majority
of
miners have already agreed to activate under segwit2x. Lastly ETC was
required to add replay protection, just like any minority fork proposed
by
any crypto-currency has been, something that BIP148 both lacks and refuses
to add or even acknowledge the necessity of. Without replay protection,
ETC
could not have become profitable enough to be a viable minority chain.
If
BIP148's chain is not the majority chain and it does not have
replay
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
protection, it will face the same problems, but that required
replay
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
protection will turn it into a hardfork. This will be a very bad position
for UASF supporters to find themselves in - Either hardfork and
hope
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
the
price is higher and the majority converts, or die as the minority chain
with
no reliable methods of economic conversion.
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction. BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there. ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
Post by James Hilliard via bitcoin-dev
I believe, but don't have data to back this, that most of the
BIP148
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
insistence comes not from a legitimate attempt to gain consensus
(or
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
else
they would either outright oppose segwit2mb for its hardfork, or
they
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
would
outright support it), but rather from an attempt for BIP148
supporters
to
save face for BIP148 being a failure. If I'm correct, that's a terrible
and
highly non-technical reason for segwit2mb to bend over backwards attempting
to support BIP148's attempt to save face.
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed
back
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
any further.
Even if I'm not correct on the above, I and others find it hard to accept
that this timeline conflict is segwit2x's fault. Segwit2x has both some
flexibility and broad support that crosses contentious pro-segwit
and
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
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pro-blocksize-increase divisions that have existed for two years.
BIP148 is
attempting to hold segwit2x's timelines and code hostage by
claiming
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inflexibility and claiming broad support, and not only are neither
of
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those
assertions are backed by real data, BIP148 (by being so inflexible) is
pushing a position that deepens the divides between those groups.
For
there
to be technical reasons for compatibility (so long as there are tradeoffs,
which there are), there needs to be hard data showing that BIP148
is
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a
viable minority fork that won't simply die off on its own.
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to
delay
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BIP91 activation, this is especially a problem since it takes a good
deal of time to properly code and test a HF. Unfortunately segwit2x
has been quite inflexible in regards to the bundling aspect even
though there are clearly no technical reasons for it to be there.
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Jared
On Wed, Jun 7, 2017 at 3:23 PM, James Hilliard
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On Wed, Jun 7, 2017 at 4:50 PM, Jared Lee Richardson
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Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?
It's fairly trivial for miners to signal for BIP91 on bit4 or a
different bit at the same time as the code is trivial enough to
combine
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The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a more
standard approach to activation that requires stronger consensus and
may be more forgiving than BIP148. If the segwit2x activation
is
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on
time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on that
idea? It may add more complexity and more developer time, but
may
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also address your concerns among others.
This does give miners another approach to activate segwit ahead of
BIP148, if segwit2x activation is rolled out and activated immediately
then this would not be needed however based on the timeline here
https://segwit2x.github.io/ it would not be possible for BIP91 to
enforce mandatory signalling ahead of BIP148. Maybe that can be
changed though, I've suggested an immediate rollout with a placeholder
client timeout instead of the HF code initially in order to accelerate
that.
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Since this BIP
only activates with a clear miner majority it should not
increase
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the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving BIP148
a sense of safety that may not be valid. Without several more steps,
BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain. (Unless
the segwit2x compromise falls apart before then, and even in
that
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case
it is likely to be a minority chain)
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain
split
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unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice) however there may be lag time immediately after the
split if there is an economic majority but not a hashpower
majority
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initially. This is risk mitigation that only requires miners
support
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however. The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed
back
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any further.
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Jared
On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to
provide
a
risk mitigation measure that miners can safely deploy. Since
this
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BIP
only activates with a clear miner majority it should not
increase
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the
risk of an extended chain split. At this point it is not completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until
BIP148
activation. I intentionally used a shorter activation period
here
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so
that decisions by miners can be made close to the BIP148 activation
date.
On Wed, Jun 7, 2017 at 4:29 PM, Jared Lee Richardson
I think this BIP represents a gamble, and the gamble may not
be
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a
good
one. The gamble here is that if the segwit2x changes are
rolled
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out
on time, and if the signatories accept the bit4 + bit1
signaling
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proposals within BIP91, the launch will go smoother, as intended.
But
conversely, if either the segwit2x signatories balk about the
Bit1
signaling OR if the timelines for segwit2mb are missed even
by a
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bit,
it may cause the BIP148 chainsplit to be worse than it would
be
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without. Given the frequent concerns raised in multiple
places
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about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble
to
be
making.
The reason I say it may make the chainsplit be worse than it
would
otherwise be is that it may provide a false sense of safety
for
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BIP148
that currently does not currently exist(and should not, as it
is
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a
chainsplit). That sense of safety would only be legitimate if
the
segwit2x signatories were on board, and the segwit2x code
effectively
enforced BIP148 simultaneously, neither of which are
guaranteed.
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If
users and more miners had a false sense that BIP148 was *not*
going
to
chainsplit from default / segwit2x, they might not follow the
news
if
suddenly the segwit2x plan were delayed for a few days. While
any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal
would
take BIP148 from the "unlikely to have any viable chain after
flag
day
without segwit2x" category into the "small but viable minority
chain"
category, and even worse, it might strengthen the chainsplit just
days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the
client,
and if BIP148 support were much much broader, I would feel
differently
as the gamble would be more likely to discourage a chainsplit (By
forcing the acceleration of segwit2x) rather than encourage it
(by
strengthening an extreme minority chainsplit that may wind up
on
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the
wrong side of two segwit-activated chains). As it stands now,
this
seems like a very dangerous attempt to compromise with a small
but
vocal group that are the ones creating the threat to begin
with.
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Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/)
for
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the
SegWit2x agreement being too slow to activate SegWit
mandatory
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signalling ahead of BIP148 using BIP91 I would like to
propose
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another
option that miners can use to prevent a chain split ahead of
the
Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using
BIP8
instead of BIP9 with a lower activation threshold and
immediate
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mandatory signalling lock-in. This allows for a majority of
miners
to
activate mandatory SegWit signalling and prevent a potential
chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces
quickly
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ahead
of BIP148 activation by signalling for splitprotection. Any
miners
already running BIP148 should be encouraged to use
splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple
majority
of miners to prevent a chain split ahead of BIP148
activation.
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==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit"
deployment
using bit 1, between November 15th 2016 and November 15th
2017
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to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this
BIP
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provides a way for a simple majority of miners to eliminate
that
risk.
This BIP provides a way for a simple majority of miners to
coordinate
activation of the existing segwit deployment with less than
95%
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hashpower before BIP148 activation. Due to time constraints
unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation
of
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BIP148. This BIP provides a method for rapid miner activation
of
SegWit mandatory signalling ahead of the BIP148 activation
date.
Since
the primary goal of this BIP is to reduce the chance of an
extended
chain split as much as possible we activate using a simple
miner
majority of 65% over a 504 block interval rather than a
higher
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percentage. This BIP also allows miners to signal their
intention
to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion
header
top
3 bits to 001 together with bit field (1<<1) (according to
the
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existing segwit deployment). Blocks that do not signal as
required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this
can
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be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork
since
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mandatory signalling will start on midnight August 1st 2017
(epoch
time 1501545600) regardless of whether or not this BIP has
reached
its
own signalling threshold. This BIP will cease to be active
when
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segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev,
chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())
)
//
and is not active.
{
bool fVersionBits = (pindex->nVersion &
VERSIONBITS_TOP_MASK)
==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed
block
must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017
00:00:00
UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017
00:00:00
UTC
(!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion &
VERSIONBITS_TOP_MASK)
==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed
block
must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...
jameshilliard:splitprotection-v0.14.1
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==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit
1
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deployment scheduled between midnight November 15th, 2016 and
midnight
November 15th, 2017. This deployment is also compatible with
the
existing BIP148 deployment. This BIP is compatible with BIP91
only
if
BIP91 activates before it and before BIP148. Miners will need
to
upgrade their nodes to support splitprotection otherwise they
may
build on top of an invalid block. While this bip is active
users
should either upgrade to splitprotection or wait for
additional
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confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft
forks
such as BIP66 which has a mandatory signalling requirement
for
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miners
once activated, this ensures that miners are aware of new
rules
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being
enforced. This technique can be leveraged to lower the
signalling
threshold of a soft fork while it is in the process of being
deployed
in a backwards compatible way. We also use a BIP8 style
timeout
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to
ensure that this BIP is compatible with BIP148 and that
BIP148
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compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1
"segwit"
deployment, this BIP can cause the existing "segwit"
deployment
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to
activate without needing to release a new deployment. As we
approach
BIP148 activation it may be desirable for a majority of
miners
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to
have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/
bitcoin-dev/2017-March/013714.html
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Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.
cpp#L1281-L1283
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P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and
delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus
layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature
Verification
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for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit
deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second
deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/
Segwit
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benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative
Commons
CC0 1.0 Universal.
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-
dev
James Hilliard via bitcoin-dev
2017-06-08 09:20:28 UTC
Permalink
Raw Message
Post by James Hilliard via bitcoin-dev
If you're looking for hard numbers at this point you aren't likely to
find them because not everything is easy to measure directly.
There's quite a few hard numbers that are available that are of varying use.
Mining commitments are a major one because of the stalled chain problem.
Node signaling represents some data because while it can be sybiled, they
are cheap but not free to run. Upvotes and comments on reddit and other
forums might be of some use, but there's not a clear supermajority driving
every pro-uasf comment up and every anti-uasf comment down, and Reddit
obscures the upvote/downvotes pretty well. It could be a gleaned datapoint
if someone pulled the comments, manually evaluated their likely position on
the matter(neutrally), and then reported on it, but that is a lot of work
and I think it is unlikely to show anything except how deep the rifts in the
community are. Of the two main statistics available, they do not support
the idea that UASF has any chance of success. Of the third, it at least
shows that there is deep opposition that is nearly equal to the support
amongst the forums most likely to support UASF.
Right, it's not straight forward to measure because the hard numbers
that we do have tell an incomplete story. In addition the metric that
BIP148 primarily depends on(economic support) is much harder to
measure than other metrics such as hashpower support.
So I'll take anything, any statistic that actually indicates UASF has a
chance in hell of succeeding, at least that would be worth something.
Otherwise it's all much ado about nothing.
Post by James Hilliard via bitcoin-dev
We'll know more as we get closer to BIP148 activation by looking at the markets.
What markets? Where? How would we know?
There will likely be some exchanges offering markets for each side of
a potential split separately ahead of BIP148 activation.
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
It doesn't have those issues during the segwit activation, ergo there is no
reason for segwit-activation problems to take priority over the very real
hardfork activation problems.
And yet segwit2x is insisting on activation bundling which needlessly
complicates and delays SegWit activation.
Because it is not segwit that has appears to have the supermajority
consensus.
I think you've misunderstood the situation, SegWit has widespread
support but has been turned into a political bargaining chip for other
less desirable changes that do not have widespread support.
Post by James Hilliard via bitcoin-dev
Sure, technical changes can be made for political reasons, we should
at least be clear in regards to why particular decisions are being
made. I'm supportive of a hard fork for technical reasons but not
political ones as are many others.
Well, then we have a point of agreement at least. :)
Post by James Hilliard via bitcoin-dev
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Not really, there are a few relatively simple techniques such as RBF
which can be leveraged to get confirmations on on-side before double
spending on another. Once a transaction is confirmed on the non-BIP148
chain then the high fee transactions can be made on only the BIP148
side of the split using RBF.
Ah, so the BIP148 client handles this on behalf of its less technical users
on their behalf then, yes?
It's not automatic but exchanges will likely handle it on behalf of
the less technical users. BIP148 is not intended to cause a permanent
chain split however which is why this was not built in.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Exchanges will likely do this splitting
automatically for uses as well.
Sure, Exchanges are going to dedicate hundreds of developer hours and
thousands of support hours to support something that they've repeatedly told
everyone must have replay protection to be supported. They're going to do
this because 8% of nodes and <0.5% of miners say they'll be rewarded richly.
Somehow I find that hard to believe.
They are very likely to, most have contingency plans for this sort of
thing ready to go due to their experience with the ETH/ETC fork.
Post by Jared Lee Richardson via bitcoin-dev
Besides, if the BIP148 client does it for them, they wouldn't have to
dedicate those hundreds of developer hours. Right?
I can't imagine how this logic is getting you from where the real data is to
the assumption that an economic majority will push BIP148 into being such a
more valuable chain that switching chains will be attractive to enough
miners. There's got to be some real data that convinces you of this
somewhere?
If you're looking for hard numbers at this point you aren't likely to
find them because not everything is easy to measure directly.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Both are issues, but wipeout risk is different, the ETH/ETC split for
example didn't have any wipeout risk for either side the same is not
true for BIP148(and it is the non-BIP148 side that carries the risk of
chain wipeout).
Wipeout risk is a serious issue when 45% of the miners support one chain and
55% support the other chain. Segwit doesn't even have 35% of the miners;
There's no data or statements anywhere that indicate that UASF is going to
reach the point where wipeout risk is even comparable to abandonment risk.
It's mostly economic support that will dictate this, not hashpower
support since the hashpower follows the economy.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Yes, miners aren't likely to waste operational mining costs, that's
ultimately why miners would follow the BIP148 side of the chain
assuming it has sufficient economic support or if it's more profitable
to mine.
To convince miners you would have to have some data SOMEWHERE supporting the
economic majority argument. Is there any such data?
We'll know more as we get closer to BIP148 activation by looking at the markets.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
segwit2x has more issues since the HF part requires users to reach consensus
It doesn't have those issues during the segwit activation, ergo there is no
reason for segwit-activation problems to take priority over the very real
hardfork activation problems.
And yet segwit2x is insisting on activation bundling which needlessly
complicates and delays SegWit activation.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
That's a political reason not a technical reason.
In a consensus system they are frequently the same, unfortunately.
Technical awesomeness without people agreeing = zero consensus. So the
choice is either to "technically" break the consensus without a
super-majority and see what happens, or to go with the choice that has real
data showing the most consensus and hope the tiny minority chain actually
dies off.
Sure, technical changes can be made for political reasons, we should
at least be clear in regards to why particular decisions are being
made. I'm supportive of a hard fork for technical reasons but not
political ones as are many others.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 5:01 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 6:43 PM, Jared Lee Richardson
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there.
This statement is misleading. Wipeout risks don't apply to any consensus
changes; It is a consensus change, it can only be abandoned. The BIP148
chain carries just as many risks of being abandoned or even more with
segwit2x on the table. No miner would consider "wipeout risk" an advantage
when the real threat is chain abandonment.
Both are issues, but wipeout risk is different, the ETH/ETC split for
example didn't have any wipeout risk for either side the same is not
true for BIP148(and it is the non-BIP148 side that carries the risk of
chain wipeout).
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction.
Higher transaction fees suffers the same problem as exchange support does.
Without replay protection, it is very difficult for any average user to
force transactions onto one chain or the other. Thus, without replay
protection, the UASF chain is unlikely to develop any viable fee market;
Its
few miners 99% of the time will simply choose from the highest fees that
were already available to the other chain, which is basically no advantage
at all.
Not really, there are a few relatively simple techniques such as RBF
which can be leveraged to get confirmations on on-side before double
spending on another. Once a transaction is confirmed on the non-BIP148
chain then the high fee transactions can be made on only the BIP148
side of the split using RBF. Exchanges will likely do this splitting
automatically for uses as well.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
ETC replay protection was added because they were already a hardfork and
without it they would not have had a viable chain. BIP148 is not supposed
to be a hardfork, and if it added replay protection to remain viable it
would lose the frequently touted "wipeout advantage" as well as the ability
to call itself a softfork. And are you seriously suggesting that what
happened with ETC and ETH is a desirable and good situation for Bitcoin,
and
that UASF is ETC?
There wasn't proper replay protection at split time for ETH/ETC since
normal transactions would get executed on both sides originally,
however replay protection was added by wallets(mainly using splitting
contracts). I don't think a split is desirable however, which is why
I've proposed this BIP.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
For a miners blowing through six million dollars a day in mining operational
costs, that's a pretty crappy reason. Serious miners can't afford to prop
up a non-viable chain based on philosophy or maybes. BIP148 is based
entirely upon people who aren't putting anything on the line trying to
convince others to take the huge risks for them. With deceptively
fallacious logic, in my opinion.
Yes, miners aren't likely to waste operational mining costs, that's
ultimately why miners would follow the BIP148 side of the chain
assuming it has sufficient economic support or if it's more profitable
to mine.
Post by Jared Lee Richardson via bitcoin-dev
Even segwit2x is based on the assumption that all miners can reach
consensus. Break that assumption and segwit2x will have the same problems
as UASF.
segwit2x has more issues since the HF part requires users to reach consensus
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation
They are bundled. Segwit alone doesn't have the desired overwhelming
consensus, unless core wishes to fork 71% to 29%, and maybe not even that
high. That's the technical reason, and they can't be unbundled without
breaking that consensus.
That's a political reason not a technical reason.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 4:11 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 5:53 PM, Jared Lee Richardson
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice)
That's not a comparable example. ETC did not face potentially years
of
slow
blocktimes before it normalized, whereas BIP148 is on track to do exactly
that. Moreover, ETC represented a fundamental break from the majority
consensus that could not be rectified, whereas BIP148 represents only
a
minority attempt to accelerate something that an overwhelming
majority
of
miners have already agreed to activate under segwit2x. Lastly ETC was
required to add replay protection, just like any minority fork proposed
by
any crypto-currency has been, something that BIP148 both lacks and
refuses
to add or even acknowledge the necessity of. Without replay protection,
ETC
could not have become profitable enough to be a viable minority chain.
If
BIP148's chain is not the majority chain and it does not have replay
protection, it will face the same problems, but that required replay
protection will turn it into a hardfork. This will be a very bad
position
for UASF supporters to find themselves in - Either hardfork and hope
the
price is higher and the majority converts, or die as the minority chain
with
no reliable methods of economic conversion.
Higher transaction fees on a minority chain can compensate miners for
a lower price which would likely be enough to get the BIP148 chain to
a difficulty reduction. BIP148 however is a consensus change that can
be rectified if it gets more work, this would act as an additional
incentive for mine the BIP148 side since there would be no wipeout
risk there. ETC replay protection was done after the fork on an as
needed basis(there are multiple reliable techniques that can be used
to split UTXO's), the same can happen with BIP148 and it is easier to
do with Bitcoin than with the ETH/ETC split IMO.
Post by James Hilliard via bitcoin-dev
I believe, but don't have data to back this, that most of the BIP148
insistence comes not from a legitimate attempt to gain consensus
(or
else
they would either outright oppose segwit2mb for its hardfork, or they
would
outright support it), but rather from an attempt for BIP148
supporters
to
save face for BIP148 being a failure. If I'm correct, that's a terrible
and
highly non-technical reason for segwit2mb to bend over backwards
attempting
to support BIP148's attempt to save face.
A big reason BIP148 still has support is because up until SegWit
actually activates there's no guarantee segwit2mb will actually have
the necessary support to activate SegWit.
Post by James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
The main issue is just one of activation timelines, BIP91 as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Even if I'm not correct on the above, I and others find it hard to accept
that this timeline conflict is segwit2x's fault. Segwit2x has both
some
flexibility and broad support that crosses contentious pro-segwit and
pro-blocksize-increase divisions that have existed for two years.
BIP148 is
attempting to hold segwit2x's timelines and code hostage by claiming
inflexibility and claiming broad support, and not only are neither of
those
assertions are backed by real data, BIP148 (by being so
inflexible)
is
pushing a position that deepens the divides between those groups.
For
there
to be technical reasons for compatibility (so long as there are
tradeoffs,
which there are), there needs to be hard data showing that BIP148
is
a
viable minority fork that won't simply die off on its own.
This is largely an issue due to segwit2x's bundling, if the SW and HF
part of segwit2x were unbundled then there would be no reason to delay
BIP91 activation, this is especially a problem since it takes a good
deal of time to properly code and test a HF. Unfortunately segwit2x
has been quite inflexible in regards to the bundling aspect even
though there are clearly no technical reasons for it to be there.
Post by James Hilliard via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 3:23 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
On Wed, Jun 7, 2017 at 4:50 PM, Jared Lee Richardson
Post by Jared Lee Richardson via bitcoin-dev
Could this risk mitigation measure be an optional flag? And if so,
could it+BIP91 signal on a different bit than bit4?
It's fairly trivial for miners to signal for BIP91 on bit4 or a
different bit at the same time as the code is trivial enough to
combine
Post by Jared Lee Richardson via bitcoin-dev
The reason being, if for some reason the segwit2x activation cannot
take place in time, it would be preferable for miners to have a
more
standard approach to activation that requires stronger consensus
and
may be more forgiving than BIP148. If the segwit2x activation is
on
time to cooperate with BIP148, it could be signaled through the
non-bit4 approach and everything could go smoothly. Thoughts on
that
idea? It may add more complexity and more developer time, but may
also address your concerns among others.
This does give miners another approach to activate segwit ahead of
BIP148, if segwit2x activation is rolled out and activated immediately
then this would not be needed however based on the timeline here
https://segwit2x.github.io/ it would not be possible for BIP91 to
enforce mandatory signalling ahead of BIP148. Maybe that can be
changed though, I've suggested an immediate rollout with a placeholder
client timeout instead of the HF code initially in order to accelerate
that.
Post by Jared Lee Richardson via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Since this BIP
only activates with a clear miner majority it should not
increase
the
risk of an extended chain split.
The concern I'm raising is more about the psychology of giving
BIP148
a sense of safety that may not be valid. Without several more
steps,
BIP148 is definitely on track to be a risky chainsplit, and without
segwit2x it will almost certainly be a small minority chain.
(Unless
the segwit2x compromise falls apart before then, and even in
that
case
it is likely to be a minority chain)
There are 2 primary factors involved here, economic support and
hashpower either of which is enough to make a permanent chain split
unlikely, miners will mine whichever chain is most profitable(see
ETH/ETC hashpower profitability equilibrium for an example of how this
works in practice) however there may be lag time immediately after
the
split if there is an economic majority but not a hashpower majority
initially. This is risk mitigation that only requires miners support
however. The main issue is just one of activation timelines,
BIP91
as
is takes too long to activate unless started ahead of the existing
segwit2x schedule and it's unlikely that BIP148 will get pushed back
any further.
Post by Jared Lee Richardson via bitcoin-dev
Jared
On Wed, Jun 7, 2017 at 2:42 PM, James Hilliard
Post by James Hilliard via bitcoin-dev
I don't really see how this would increase the likelihood of an
extended chain split assuming BIP148 is going to have
non-insignificant economic backing. This BIP is designed to
provide
a
risk mitigation measure that miners can safely deploy. Since
this
BIP
only activates with a clear miner majority it should not
increase
the
risk of an extended chain split. At this point it is not
completely
clear how much economic support there is for BIP148 but support
certainly seems to be growing and we have nearly 2 months until
BIP148
activation. I intentionally used a shorter activation period here
so
that decisions by miners can be made close to the BIP148
activation
date.
On Wed, Jun 7, 2017 at 4:29 PM, Jared Lee Richardson
I think this BIP represents a gamble, and the gamble may not
be
a
good
one. The gamble here is that if the segwit2x changes are
rolled
out
on time, and if the signatories accept the bit4 + bit1
signaling
proposals within BIP91, the launch will go smoother, as
intended.
But
conversely, if either the segwit2x signatories balk about the
Bit1
signaling OR if the timelines for segwit2mb are missed even
by a
bit,
it may cause the BIP148 chainsplit to be worse than it would be
without. Given the frequent concerns raised in multiple places
about
the aggressiveness of the segwit2x timelines, including the
non-hardfork timelines, this does not seem like a great gamble
to
be
making.
The reason I say it may make the chainsplit be worse than it
would
otherwise be is that it may provide a false sense of safety for
BIP148
that currently does not currently exist(and should not, as it
is
a
chainsplit). That sense of safety would only be legitimate if
the
segwit2x signatories were on board, and the segwit2x code
effectively
enforced BIP148 simultaneously, neither of which are
guaranteed.
If
users and more miners had a false sense that BIP148 was *not*
going
to
chainsplit from default / segwit2x, they might not follow the
news
if
suddenly the segwit2x plan were delayed for a few days.
While
any
additional support would definitely be cheered on by BIP148
supporters, the practical reality might be that this proposal
would
take BIP148 from the "unlikely to have any viable chain after
flag
day
without segwit2x" category into the "small but viable minority
chain"
category, and even worse, it might strengthen the chainsplit
just
days
before segwit is activated on BOTH chains, putting the BIP148
supporters on the wrong pro-segwit, but still-viable chain.
If Core had taken a strong stance to include BIP148 into the
client,
and if BIP148 support were much much broader, I would feel
differently
as the gamble would be more likely to discourage a chainsplit
(By
forcing the acceleration of segwit2x) rather than encourage it
(by
strengthening an extreme minority chainsplit that may wind up
on
the
wrong side of two segwit-activated chains). As it stands now,
this
seems like a very dangerous attempt to compromise with a small
but
vocal group that are the ones creating the threat to begin
with.
Jared
On Tue, Jun 6, 2017 at 5:56 PM, James Hilliard via bitcoin-dev
Post by James Hilliard via bitcoin-dev
Due to the proposed calendar(https://segwit2x.github.io/) for
the
SegWit2x agreement being too slow to activate SegWit
mandatory
signalling ahead of BIP148 using BIP91 I would like to
propose
another
option that miners can use to prevent a chain split ahead of
the
Aug
1st BIP148 activation date.
The splitprotection soft fork is essentially BIP91 but using
BIP8
instead of BIP9 with a lower activation threshold and
immediate
mandatory signalling lock-in. This allows for a majority of
miners
to
activate mandatory SegWit signalling and prevent a potential
chain
split ahead of BIP148 activation.
This BIP allows for miners to respond to market forces
quickly
ahead
of BIP148 activation by signalling for splitprotection. Any
miners
already running BIP148 should be encouraged to use
splitprotection.
<pre>
BIP: splitprotection
Layer: Consensus (soft fork)
Title: User Activated Soft Fork Split Protection
Comments-Summary: No comments yet.
Status: Draft
Type: Standards Track
Created: 2017-05-22
License: BSD-3-Clause
CC0-1.0
</pre>
==Abstract==
This document specifies a coordination mechanism for a simple
majority
of miners to prevent a chain split ahead of BIP148
activation.
==Definitions==
"existing segwit deployment" refer to the BIP9 "segwit"
deployment
using bit 1, between November 15th 2016 and November 15th
2017
to
activate BIP141, BIP143 and BIP147.
==Motivation==
The biggest risk of BIP148 is an extended chain split, this
BIP
provides a way for a simple majority of miners to eliminate
that
risk.
This BIP provides a way for a simple majority of miners to
coordinate
activation of the existing segwit deployment with less than
95%
hashpower before BIP148 activation. Due to time constraints
unless
immediately deployed BIP91 will likely not be able to enforce
mandatory signalling of segwit before the Aug 1st activation
of
BIP148. This BIP provides a method for rapid miner activation
of
SegWit mandatory signalling ahead of the BIP148 activation
date.
Since
the primary goal of this BIP is to reduce the chance of an
extended
chain split as much as possible we activate using a simple
miner
majority of 65% over a 504 block interval rather than a
higher
percentage. This BIP also allows miners to signal their
intention
to
run BIP148 in order to prevent a chain split.
==Specification==
While this BIP is active, all blocks must set the nVersion
header
top
3 bits to 001 together with bit field (1<<1) (according to
the
existing segwit deployment). Blocks that do not signal as
required
will be rejected.
==Deployment==
This BIP will be deployed by "version bits" with a 65%(this
can
be
adjusted if desired) activation threshold BIP9 with the name
"splitprotecion" and using bit 2.
This BIP starts immediately and is a BIP8 style soft fork
since
mandatory signalling will start on midnight August 1st 2017
(epoch
time 1501545600) regardless of whether or not this BIP has
reached
its
own signalling threshold. This BIP will cease to be active
when
segwit
is locked-in.
=== Reference implementation ===
<pre>
// Check if Segregated Witness is Locked In
bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params,
Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
THRESHOLD_LOCKED_IN);
}
// SPLITPROTECTION mandatory segwit signalling.
if ( VersionBitsState(pindex->pprev,
chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
THRESHOLD_LOCKED_IN &&
!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())
)
//
and is not active.
{
bool fVersionBits = (pindex->nVersion &
VERSIONBITS_TOP_MASK)
==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed
block
must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
// BIP148 mandatory segwit signalling.
int64_t nMedianTimePast = pindex->GetMedianTimePast();
if ( (nMedianTimePast >= 1501545600) && // Tue 01 Aug 2017
00:00:00
UTC
(nMedianTimePast <= 1510704000) && // Wed 15 Nov 2017
00:00:00
UTC
(!IsWitnessLockedIn(pindex->pprev,
chainparams.GetConsensus())
&&
// Segwit is not locked in
!IsWitnessEnabled(pindex->pprev,
chainparams.GetConsensus())) )
// and is not active.
{
bool fVersionBits = (pindex->nVersion &
VERSIONBITS_TOP_MASK)
==
VERSIONBITS_TOP_BITS;
bool fSegbit = (pindex->nVersion &
VersionBitsMask(chainparams.GetConsensus(),
Consensus::DEPLOYMENT_SEGWIT)) != 0;
if (!(fVersionBits && fSegbit)) {
return state.DoS(0, error("ConnectBlock(): relayed
block
must
signal for segwit, please upgrade"), REJECT_INVALID,
"bad-no-segwit");
}
}
</pre>
https://github.com/bitcoin/bitcoin/compare/0.14...jameshilliard:splitprotection-v0.14.1
==Backwards Compatibility==
This deployment is compatible with the existing "segwit" bit
1
deployment scheduled between midnight November 15th, 2016 and
midnight
November 15th, 2017. This deployment is also compatible with
the
existing BIP148 deployment. This BIP is compatible with BIP91
only
if
BIP91 activates before it and before BIP148. Miners will need
to
upgrade their nodes to support splitprotection otherwise they
may
build on top of an invalid block. While this bip is active
users
should either upgrade to splitprotection or wait for
additional
confirmations when accepting payments.
==Rationale==
Historically we have used IsSuperMajority() to activate soft
forks
such as BIP66 which has a mandatory signalling requirement
for
miners
once activated, this ensures that miners are aware of new
rules
being
enforced. This technique can be leveraged to lower the
signalling
threshold of a soft fork while it is in the process of being
deployed
in a backwards compatible way. We also use a BIP8 style
timeout
to
ensure that this BIP is compatible with BIP148 and that
BIP148
compatible mandatory signalling activates regardless of miner
signalling levels.
By orphaning non-signalling blocks during the BIP9 bit 1
"segwit"
deployment, this BIP can cause the existing "segwit"
deployment
to
activate without needing to release a new deployment. As we
approach
BIP148 activation it may be desirable for a majority of
miners
to
have
a method that will ensure that there is no chain split.
==References==
*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html
Mailing list discussion]
*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283
P2SH flag day activation]
*[[bip-0009.mediawiki|BIP9 Version bits with timeout and
delay]]
*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
*[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus
layer)]]
*[[bip-0143.mediawiki|BIP143 Transaction Signature
Verification
for
Version 0 Witness Program]]
*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
malleability]]
*[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit
deployment]]
*[[bip-0149.mediawiki|BIP149 Segregated Witness (second
deployment)]]
*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/
Segwit
benefits]
==Copyright==
This document is dual licensed as BSD 3-clause, and Creative
Commons
CC0 1.0 Universal.
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