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From: Pieter Wuille <bitcoin-dev@wuille.net>
To: Karl-Johan Alm <karljohan-alm@garage.co.jp>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP-0322 (generic signmessage) improvements
Date: Mon, 21 Dec 2020 22:57:15 +0000	[thread overview]
Message-ID: <Xpjf4qIbUPHa_K-yS1GRlsG4rVXBR9OHgzsxjgABhw0hg7jPFn4l4wwgVH_1iRVR5jFDK2cUb0qsbA1FQKiQZRTFPh77MGibgaVUaVbB_Ng=@wuille.net> (raw)
In-Reply-To: <CALJw2w4bFp8qcxNzz7hn_ZeGG8WWTPu-mRv6A4cPt66EHimyeg@mail.gmail.com>

On Sunday, December 20, 2020 9:37 PM, Karl-Johan Alm via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:

> Thanks a lot for taking the time to brush up the BIP. For what it's
> worth, I am all for these changes, and I see them as clear
> improvements all around.
>
> IIRC Pieter was the one who originally suggested the two-checks
> approach (invalid, inconclusive, valid) which is being modified here,
> so would be good if you chimed in (or not -- which I'll assume means
> you don't mind).

I agree with the idea of permitting incomplete validators to return inconclusive as well. That doesn't really reduce the functionality (given that "inconclusive" was already a potential result), and it obviously makes it much more accessible to a variety of software.

This suggestion breaks the original use of inconclusive though: the ability to detect that future features are used in the signature. The idea was to use divergence between "consensus valid" and "standardness valid" as a proxy for future extensions to be detected (e.g. OP_NOPn, future witness versions, ...). I think it's undesirable that these things now become unconditionally invalid (until the BIP is updated, but once that happens old validators will give a different result than new ones).

Since the BIP no longer relies on a nebulous concept of standardness, and instead specifically defines which standardness features are to be considered, this seems easy to fix: whenever validation fails due to any of those, require reporting inconclusive instead of invalid (unless of course something actually invalid also happens). In practice I guess you'd implement that (in capable validators) by still doing validation twice, once with all features enabled that distinguish between valid/invalid, and if valid, again but now with the features enabled that distinguish between valid and (invalid or inconclusive).

Cheers,

--
Pieter



  reply	other threads:[~2020-12-21 22:57 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-18 15:27 [bitcoin-dev] BIP-0322 (generic signmessage) improvements Andrew Poelstra
2020-12-21  5:37 ` Karl-Johan Alm
2020-12-21 22:57   ` Pieter Wuille [this message]
2020-12-22  0:22     ` Pieter Wuille
2020-12-22  1:11       ` Andrew Poelstra
2020-12-23 15:55       ` Andrew Poelstra

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