[bitcoin-dev] Relaxing minimum non-witness transaction size policy restriction

[Greg Sanders <gsanders87@gmail.com>]

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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

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