public inbox for bitcoindev@googlegroups.com
 help / color / mirror / Atom feed

From: Rusty Russell <rusty@rustcorp•com.au>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists•linuxfoundation.org>
Subject: [bitcoin-dev] Progress on bech32 for future Segwit Versions (BIP-173)
Date: Thu, 08 Oct 2020 10:51:10 +1030	[thread overview]
Message-ID: <87imblmutl.fsf@rustcorp.com.au> (raw)

Hi all,

        I propose an alternative to length restrictions suggested by
Russell in https://github.com/bitcoin/bips/pull/945: use the
https://gist.github.com/sipa/a9845b37c1b298a7301c33a04090b2eb variant,
unless the first byte is 0.

Here's a summary of each proposal:

Length restrictions (future segwits must be 10, 13, 16, 20, 23, 26, 29,
32, 36, or 40 bytes)
  1. Backwards compatible for v1 etc; old code it still works.
  2. Restricts future segwit versions, may require new encoding if we
     want a diff length (or waste chainspace if we need to have a padded
     version for compat).
    
Checksum change based on first byte:
  1. Backwards incompatible for v1 etc; only succeeds 1 in a billion.
  2. Weakens guarantees against typos in first two data-part letters to
     1 in a billion.[1]

I prefer the second because it forces upgrades, since it breaks so
clearly.  And unfortunately we do need to upgrade, because the length
extension bug means it's unwise to accept non-v0 addresses.

(Note non-v0 segwit didn't relay before v0.19.0 anyway, so many places
may already be restricting to v0 segwit).

The sooner a decision is reached on this, the sooner we can begin
upgrading software for a taproot world.

Thanks,
Rusty.
PS. Lightning uses bech32 over longer lengths, but the checksum is less critical; we'd prefer to follow whatever
bitcoin chooses.

[1] Technically less for non-v0: you have a 1 in 8 chance of a typo in the second letter changing the checksum
     algorithm, so it's 1 in 8 billion. 

next             reply	other threads:[~2020-10-08  0:21 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-08  0:21 Rusty Russell [this message]
2020-10-08 14:59 ` David A. Harding
2020-10-08 15:21   ` Russell O'Connor
2020-10-15  1:40   ` Rusty Russell
2020-10-16 21:09     ` Pieter Wuille
2020-10-19  0:49       ` Rusty Russell
2020-10-19 22:55         ` Pieter Wuille
2020-10-20  0:42           ` Rusty Russell
2020-10-20  3:31             ` Rusty Russell
2020-10-20  9:21               ` Riccardo Casatta
2020-10-20 10:29             ` David A. Harding
2020-10-20 20:12               ` Pieter Wuille
2020-10-20 23:52                 ` Mike Schmidt
2020-10-21  4:51                   ` Rusty Russell
2020-11-06 19:49                   ` Mike Schmidt
2020-12-05 23:10                     ` Pieter Wuille
2020-12-06 13:04                       ` David A. Harding
2020-12-06 20:43                         ` Pieter Wuille
2020-12-08 17:39                         ` Ryan Grant
2020-12-18  2:02                           ` Pieter Wuille
2020-10-21  3:05         ` ZmnSCPxj
2020-10-21  4:39           ` Rusty Russell
2020-10-28  0:20 ` Pieter Wuille
2020-12-05 22:59   ` Pieter Wuille

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87imblmutl.fsf@rustcorp.com.au \
    --to=rusty@rustcorp$(echo .)com.au \
    --cc=bitcoin-dev@lists$(echo .)linuxfoundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox