Re: [Bitcoin-development] Small update to BIP 62

[Gregory Maxwell <gmaxwell@gmail.com>]

On Fri, Jul 18, 2014 at 8:14 AM, Pieter Wuille <pieter.wuille@gmail.com> wrote:
> Hi all,
>
> I've sent a pull request to make a small change to BIP 62 (my
> anti-malleability proposal) which is still a draft; see:
> * https://github.com/bitcoin/bips/pull/90 (the request)
> * https://github.com/sipa/bips/blob/bip62up/bip-0062.mediawiki (the result)
>
> It makes two of the 7 new rules mandatory in new blocks, even for
> old-style transactions. Both are already non-standard since 0.8.0, and
> have no use cases in my opinion.
>
> The reason for this change is dropping the requirement for signature
> verification engines to be bug-for-bug compatible with OpenSSL (which
> supports many non-standard encodings for signatures). Requiring strict
> DER compliance for signatures means any implementation just needs to
> support DER.

Not related to this change but the definition of rule 4 may not be
sufficiently specific— without a definition someone could reasonably
reach a different conclusion about OP_1NEGATE being a "push
operation", or might even decide any operation which added to the
stack was a "push operation".

Any particular reason to enforce 2 and 4 but not also 5?  Violation of
5 is already non-standard and like 2,4 should be safely enforceable.

Perhaps the rules should be reordered so that the applicable to all
transactions ones are contiguous and first?

> The first six and part of the seventh can be fixed by extra consensus rules.

This should clarify that the scriptPubkey can still specify rules that
are inherently malleable— e.g. require the input stack contain two
pushes which OP_ADD to 11.  Or a more elaborate one— a 1 of 2 check
multisig where the pubkey not selected for signing is selected by a
push in the signature. The current text seems to ignore isomorphisms
of this type. ... they're not important for what the BIP is trying to
achieve, but the document shouldn't cause people to not think that
sort of thing exists.