public inbox for bitcoindev@googlegroups.com
 help / color / mirror / Atom feed
From: Ali Sherief <ali@notatether.com>
To: Pieter Wuille <bitcoin-dev@wuille.net>
Cc: "bitcoin-dev@lists.linuxfoundation.org"
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Zero-knowledge proofs e.g. Schnorr are incompatible with address signing without compromise
Date: Thu, 28 Jul 2022 15:51:18 +0000	[thread overview]
Message-ID: <ltMy8y1N-J_DQ0rQiKcb1fkiBkd9PcLX6B4W_TZ6i7bdmNWQMXJ0h2fet6DFKvllyH0QNzzVnqMpxT3vMgxdwJKOfsUKf8lS5P5sTC4-3j8=@notatether.com> (raw)
In-Reply-To: <BQZI2zpZwzJcXi_Gxr0f1wg9ZD6U5nb0HTOfIu4i50nM6FqFNqFjfm4DbOIxg94IwZQ4pHAthUNeGUkwHENJwAhap-bIkuKRN8ErZyFeR-o=@wuille.net>

> Yes, that's an intentional design choice in BIP340, see note 5: https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki#cite_ref-5-0. The choice is either batch verifiability or public key recovery.

The way I understood the BIP, was that a user can do batch recovery or single-key recovery. Can you explain how it is possible to recover a public key from a single-key signature, because a few days earlier on the BIP-notatether-messageverify thread I was told (I think it was achow) that Schnorr doesn't allow for public key recovery.

At any case, I was already planning on just concatenating the public key after the signature (the other option I was thinking of, appending it after the Taproot address, is quite unruly in my opinion).

> I think it would be much better if people would cooperate to get BIP322 to move forward than to keep inventing other formats. It's the obvious solution in my opinion: not restricted to single-key policies, compatible with every script type, and trivially extensible to future schemes.

This is why I especially tried to avoid making a new format - My BIP is strictly an Informational one. That strategy worked pretty well up to now, but now I find myself forced to make a small concession in the design to support the verification of Taproot address. But I'm glad it's quite trivial as appending a single variable. So at least this BIP won't be an obstacle to any such effort.

[Besides, since I'm also planning on detecting BIP137 in the verification methods, I can assume the Signature field contains arbitrary data.]

> > , just like BIP340).
>
>
> How so? Every taproot compatible wallet has a BIP340 implementation.

I guess I made an assumption, since almost all of the wallets I have seen did not have a sign message feature, not even for legacy addresses.

- Ali

------- Original Message -------
On Thursday, July 28th, 2022 at 3:27 PM, Pieter Wuille <bitcoin-dev@wuille.net> wrote:


> ------- Original Message -------
> On Thursday, July 28th, 2022 at 3:27 AM, Ali Sherief via bitcoin-dev bitcoin-dev@lists.linuxfoundation.org wrote:
>
> > Essentially, zero-knowledge proofs such as Schnorr are not compatible with address message signing - the public key cannot be retrieved from the address or the signature, so the address does not actually prove the authenticity of a Schnorr signature. That's why the public key is required as an input in the first place.
>
>
> Yes, that's an intentional design choice in BIP340, see note 5: https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki#cite_ref-5-0. The choice is either batch verifiability or public key recovery.
>
> I regret ever using public key recovery when introducing the old legacy message signing scheme. It should just have used script signatures like BIP322 proposes.
>
> > In order to make it compatible with the address signing mechanism, the zero-knowledge part would have to be sacrificed in my BIP, or else a completely separate message signing format just for Taproot would be required
>
>
> You can avoid relying on public key recovery, and include the public key + BIP340 signature in the encoded signature.
>
> > (which, in my view, is redundant - there is already the draft BIP322 which can verify anything and everything, but nobody is implementing that
>
>
> I think it would be much better if people would cooperate to get BIP322 to move forward than to keep inventing other formats. It's the obvious solution in my opinion: not restricted to single-key policies, compatible with every script type, and trivially extensible to future schemes.
>
> > , just like BIP340).
>
>
> How so? Every taproot compatible wallet has a BIP340 implementation.
>
> Cheers,
>
> --
> Pieter


  reply	other threads:[~2022-07-28 15:51 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-28  7:27 [bitcoin-dev] Zero-knowledge proofs e.g. Schnorr are incompatible with address signing without compromise Ali Sherief
2022-07-28 15:27 ` Pieter Wuille
2022-07-28 15:51   ` Ali Sherief [this message]
2022-07-28 15:58     ` 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='ltMy8y1N-J_DQ0rQiKcb1fkiBkd9PcLX6B4W_TZ6i7bdmNWQMXJ0h2fet6DFKvllyH0QNzzVnqMpxT3vMgxdwJKOfsUKf8lS5P5sTC4-3j8=@notatether.com' \
    --to=ali@notatether.com \
    --cc=bitcoin-dev@lists.linuxfoundation.org \
    --cc=bitcoin-dev@wuille.net \
    /path/to/YOUR_REPLY

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

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox