I am reading between the lines, wouldn't that mean an older client like v0.18 may not be able to receive a transaction from a newer client if it has to validate 85 non-witness serialized bytes? If so we should not concern but retain the backward compatibility especially since this was for a vulnerability? I have not checked to code to see what it does.

KING JAMES HRMH

Get Outlook for Android

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From: bitcoin-dev <bitcoin-dev-bounces@lists.linuxfoundation.org> on behalf of Greg Sanders via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>
Sent: Tuesday, October 11, 2022 11:50:07 PM
To: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: [bitcoin-dev] Relaxing minimum non-witness transaction size policy restriction

 

Hello fellow Bitcoiners,

After looking at some fairly exotic possible transaction types, I ran into the current policy limit requiring transactions to be 85 non-witness serialized bytes. This was introduced as a covert fix to policy fix for CVE-2017-12842. Later the real motivation was revealed, but the "reasonable" constant chosen was not.

I'd like to propose relaxing this to effectively the value BlueMatt proposed in the Great Consensus Cleanup: 65 non-witness bytes. This would allow a single input, single output transaction with 4 bytes of OP_RETURN padding, rather than padding out 21 bytes to get to p2wpkh size.

The alternative would be to also allow anything below 64 non-witness bytes, but this seems fraught with footguns for a few bytes gain.

The PR is here with more relevant background and alternatives included in the thread:

https://github.com/bitcoin/bitcoin/pull/26265

Please let us know if there's a fundamental issue with this approach, or any other feedback.

Best,

Greg