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From: Mark Friedenbach <mark@friedenbach.org>
In-Reply-To: <52b65bab-ff84-7e21-e35a-f6ebd8106767@satoshilabs.com>
Date: Tue, 19 Dec 2017 13:58:40 -0800
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References: <CAAUFj10gEPBS3nTZ6aJn4UazhcJKPni6_pYGWwOs+QNeDo9NaA@mail.gmail.com>
	<52b65bab-ff84-7e21-e35a-f6ebd8106767@satoshilabs.com>
To: Pavol Rusnak <stick@satoshilabs.com>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Sign / Verify message against SegWit P2SH
 addresses.
Precedence: list

For what it=E2=80=99s worth, I think it would be quite easy to do better =
than the implied solution of rejiggering the message signing system to =
support non-P2PKH scripts. Instead, have the signature be an actual =
bitcoin transaction with inputs that have the script being signed. Use =
the salted hash of the message being signed as the FORKID as if this =
were a spin-off with replay protection. This accomplishes three things:

(1) This enables signing by any infrastructure out there =E2=80=94 =
including hardware wallets and 2FA signing services =E2=80=94 that have =
enabled support for FORKID signing, which is a wide swath of the =
ecosystem because of Bitcoin Cash and Bitcoin Gold.

(2) It generalizes the message signing to allow multi-party signing =
setups as complicated (via sighash, etc.) as those bitcoin transactions =
allow, using existing and future tools based on Partially Signed Bitcoin =
Transactions; and

(3) It unifies a single approach for message signing, proof of reserve =
(where the inputs are actual UTXOs), and off-chain colored coins.

There=E2=80=99s the issue of size efficiency, but for the single-party =
message signing application that can be handled by a BIP that specifies =
a template for constructing the pseudo-transaction and its inputs from a =
raw script.

Mark

> On Dec 19, 2017, at 1:36 PM, Pavol Rusnak via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:
>=20
> On 08/12/17 19:25, Dan Bryant via bitcoin-dev wrote:
>> I know there are posts, and an issue opened against it, but is there
>> anyone writing a BIP for Sign / Verify message against a SegWit =
address?
>=20
> Dan, are you still planning to write this BIP?
>=20
> --=20
> Best Regards / S pozdravom,
>=20
> Pavol "stick" Rusnak
> CTO, SatoshiLabs
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev