Discussion:
[RFC] Lightning invoice/payment format draft
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Rusty Russell via bitcoin-dev
2017-06-01 01:28:20 UTC
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Hi all,

There's a pull request for a lightning payment format which I'd
love wider review on. It's bech32 encoded, with optional parts tagged:

https://github.com/lightningnetwork/lightning-rfc/pull/183

There's an implementation with a less formal description here, too:

https://github.com/rustyrussell/lightning-payencode

Example:
Send 2500 microbitcoin using payment hash 00010203040506...0102 to me
@03e7156ae33b0a208d0744199163177e909e80176e55d97a2f221ede0f934dd9ad
within 1 minute from now (Tue 30 May 12:17:36 UTC 2017):

lnbc2500u1qpvj6chqqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdq5xysxxatsyp3k7enxv4jsxqz8slk6hqew9z5kzxyk33ast248j3ykmu3wncvgtgk0ewf5c6qnhen45vr43fmtzsh02j6ns096tcpfga0yfykc79e5uw3gh5ltr96q00zqppy6lfy

Thanks!
Rusty.
ZmnSCPxj via bitcoin-dev
2017-06-01 03:42:21 UTC
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Good morning Rusty,

The fact that amount is optional, and the separator character between human-readable and data is the character "1", may mean some trouble with parsing of the optional amount.

Currently, the version is 0, which translates to the character "q" appearing after "1". So 1q is obviously not an amount and is known to start the data part.

However, what happens when we decide to upgrade, and version is now 1, translating to character "p"?

If version 1 of invoice is avalialble, does a payment starting with lnbc1p .... indicate a 1 pico-bitcoin payment, or an arbitrary payment to a version-1 data part?

Or is amount not allowed to have character "1"? It seems a strange limitation if we impose this...

Or do I mistake my understanding of bech32?

Alternatively we can just fix the first 5 bits to be 0 (so "1q" is an unambiguous separator between human-readable and data parts) and provide the version by other means, such as changing lnbc to ln2bc or so on...
simply reused here even though its 6-character checksum is optimized
for human errors, which are unlikely given the length of lightning
invoices.
At first read, this seems wrong. My understanding is that lightning invoices are longer than segwit addresses in bech32, so human error is more likely.

Of course, it seems that the intended meaning is really "lightning invoices are so long that it is unlikely humans will enter it by hand, so human errors are unlikely compared to QR reader errors etc." so perhaps better reworded as such.

Regards,
ZmnSCPxj
ZmnSCPxj via bitcoin-dev
2017-06-01 03:48:46 UTC
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Good morning,
Post by ZmnSCPxj via bitcoin-dev
Or do I mistake my understanding of bech32?
Looking again at bech32 spec, yes, my understanding is wrong: the character "1" is not allowed in the data part, so the last "1" digit in the bech32 string is unambiguously the separator between the human-readable and data parts, please ignore me.

Regards,
ZmnSCPxj
Andreas Schildbach via bitcoin-dev
2017-06-01 05:54:37 UTC
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In order for such messages to be dispatchable between apps, I suggest
prepending with an URI scheme, similar to the already existing
"bitcoin:" scheme.

Also I suggest defining a MIME type, e.g. for usage in NFC NDEF messages
or emails.

What is the relation of this BIP to BIP21 and BIP70-72? Is there a
reason for not extending BIP70?
Post by Rusty Russell via bitcoin-dev
Hi all,
There's a pull request for a lightning payment format which I'd
https://github.com/lightningnetwork/lightning-rfc/pull/183
https://github.com/rustyrussell/lightning-payencode
Send 2500 microbitcoin using payment hash 00010203040506...0102 to me
@03e7156ae33b0a208d0744199163177e909e80176e55d97a2f221ede0f934dd9ad
lnbc2500u1qpvj6chqqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdq5xysxxatsyp3k7enxv4jsxqz8slk6hqew9z5kzxyk33ast248j3ykmu3wncvgtgk0ewf5c6qnhen45vr43fmtzsh02j6ns096tcpfga0yfykc79e5uw3gh5ltr96q00zqppy6lfy
Thanks!
Rusty.
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