Re: [bitcoin-dev] Trying all address types in message signing verification (BIP)

From: Craig Raw <craigraw@gmail•com>
To: Greg Sanders <gsanders87@gmail•com>,
	 Bitcoin Protocol Discussion
	<bitcoin-dev@lists•linuxfoundation.org>
Cc: Ali Sherief <ali@notatether•com>, Peter <peter@coinkite•com>
Subject: Re: [bitcoin-dev] Trying all address types in message signing verification (BIP)
Date: Thu, 21 Jul 2022 09:06:08 +0200	[thread overview]
Message-ID: <CAPR5oBMF0WdzDFnytLJjE205KUYR_WGVUxJ5AjwU-0KZgwvkOA@mail.gmail.com> (raw)
In-Reply-To: <CAB3F3Du0OXcUvi6h8v0VZEj4cG24DJs04Vho8sM4Frhdhj5DrA@mail.gmail.com>

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> Unfortunately, I do not know of any "verifiers" that will accept the
above signature

Sparrow verifies this signature.

The approach used is to convert the message and signature to a public key,
trying first BIP137 and then the approach used by Electrum (they differ in
treatment of the signature header for segwit P2SH). The script type is
extracted from the provided address and compared against the address
constructed with the public key using the same script type. i.e. There is
no need to iterate through all script types, since the script type is
implicitly provided in the address.

Craig

On Wed, Jul 20, 2022 at 11:51 PM Greg Sanders via bitcoin-dev <
bitcoin-dev@lists•linuxfoundation.org> wrote:

> Please see BIP322
> https://github.com/bitcoin/bips/blob/master/bip-0322.mediawiki
>
> On Wed, Jul 20, 2022, 5:46 PM Peter (Coinkite Inc) via bitcoin-dev <
> bitcoin-dev@lists•linuxfoundation.org> wrote:
>
>> Hi Ali.
>>
>> > This BIP does not replace, supersede, or obsolete BIPs 173 or 322. My
>> proposal is simply going to standardize the practice of placing the segwit
>> address into the address field, and does not require alterations to the
>> message signing format like those BIPs.
>>
>> COLDCARD makes signatures exacly like that, when told to sign with a
>> segwit address:
>>
>>     % ckcc msg -s Hello
>>     Hello
>>     bc1qzeacswvlulg0jngad9gmtkvdp9lwum42wwzdu5
>>
>> HxuuWQwjw0417fLV9L0kWbt7w9XOIWKhHMhjXhyXTczcSozGTXM4knqdISiYbbmqSRXqI5mNTWH9qkDoqZTpnPc=
>>
>> Unfortunately, I do not know of any "verifiers" that will accept the
>> above signature, but there is no alternative since the various BIP-322
>> proposals never gained wide acceptance.
>>
>> Bitcoin Core does not support verifying that message, even though the UX
>> makes it look possible. In effect segwit features never got implemented to
>> that depth in Core. It's sad because the community is not maintaining core
>> (Core?) features to the same depth as Satoshi did when he was active in the
>> project.
>>
>> > PS. I am pretty sure that there is a BIP for the original signing
>> method - what is its number?
>>
>> My understanding that the original approach was directly from Satoshi
>> himself when the original client was written. It has never been codified in
>> a BIP as far as I know.
>>
>> A related issue the the "ascii armor" that is sometimes used. It's a
>> little like RFC2440 <https://www.ietf.org/rfc/rfc2440.txt> but
>> newline-treatment isn't defined well enough for good interoperability, in
>> my personal experience.
>>
>> So in summary... yes a "defacto" BIP is needed and useful to do, in my
>> opinion. Then Core should be updated to support it as well.
>>
>> ---
>> @DocHEX  ||  Coinkite  ||  PGP: A3A31BAD 5A2A5B10
>>
>>
>> On Wed, Jul 20, 2022 at 04:10:09AM +0000, Ali Sherief wrote:
>> > [my third attempt at getting this message through. Surprisingly, I
>> managed to send this at the second try with the correct SMTP, From, To and
>> all, but maybe it was caught in GreyListing (protonmail).]
>> >
>> > I was thinking about creating a BIP to address the lack of
>> standardization for Segwit message signatures, but I want some advice
>> before proceeding.
>> >
>> > The current state of affairs is that the wallets that do support
>> signing and verifying a bitcoin message can only sign legacy addresses. It
>> is technically possible to sign and verify segwit addresses, since ECDSA
>> only depends on the public key (hence why you need a private key to sign
>> messages).
>> >
>> > However, because there is no generally-accepted standard for signing
>> segwit messages, the wallets that do support this feature simply insert the
>> segwit address into the address field. Verification also only works using
>> the procedure on that specific wallet software, if only because the
>> conventional tools for verifying messages attempt to reconstruct a legacy
>> address only.
>> >
>> > This BIP is not going to enforce anything, it's just going to set
>> guidelines for writing a message signing and verification procedure.
>> >
>> > This BIP does not replace, supersede, or obsolete BIPs 173 or 322. My
>> proposal is simply going to standardize the practice of placing the segwit
>> address into the address field, and does not require alterations to the
>> message signing format like those BIPs.
>> >
>> > In summary, in the verification part, the following address hashing
>> algorithms will be tried in sequence in an attempt to reconstruct the
>> address in the signed message:
>> > - P2PKH (legacy address)
>> > - P2WPKH-P2SH (nested segwit)
>> > - P2WPKH with version from 0 to MAX_WITNESS_VERSION (covers native
>> segwit with version 0 as well as future native segwit address types such as
>> Taproot) - where MAX_WITNESS_VERSION is the maximum supported witness
>> version by the bech32 encoding.
>> >
>> > The verification procedure stops if any of these hashes yield the
>> correct address, and fails if all of the above methods fail to reproduce
>> the address in the signed message.
>> >
>> > In the signing procedure, the only modification is the insertion of the
>> segwit address in place of the legacy address in the signed message.
>> >
>> > If this BIP is approved, it does not require any changes to existing
>> signed messages, and the original sign/verify algorithms will continue to
>> interoperate with this improved sign/verify algorithm, without any action
>> necessary from the developers.
>> >
>> > So as you can see, this is the entire framework of the BIP I plan to
>> draft. There is no need for any auxilliary feature additions into this BIP.
>> I just want to hear the mailing list's advice about how I should draft such
>> a BIP.
>> >
>> > - Ali
>> >
>> > PS. I am pretty sure that there is a BIP for the original signing
>> method - what is its number?
>> >
>>
>>
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