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To: Pieter Wuille <bitcoin-dev@wuille.net>
From: Dr Maxim Orlovsky <orlovsky@protonmail.com>
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X-Mailman-Approved-At: Thu, 18 Feb 2021 19:36:58 +0000
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP32/43-based standard for Schnorr signatures &
decentralized identity
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Hi Pieter,
Addressing your comments:
>> Thank you very much for all the clarifications; it=E2=80=99s good to hav=
e them sorted out and clearly structured. From what you wrote it follows th=
at we still need to reserve a dedicated purpose (with new BIP) for BIP340 s=
ignatures to avoid key reuse, am I right?
>=20
> Maybe, but it would be for a particular way of using keys (presumably: si=
ngle-key pay-to-taproot), not just the signature scheme itself. If you go d=
own this path you'll also want dedicated branches for multisig participatio=
n, and presumably several interesting new policies that become possible wit=
h Taproot.
Yes, previously we had a dedicated standards (BIPs) for purpose fields on e=
ach variant: single-sig, multi-sig etc. With this proposal I simplify this:=
you will have a dedicated deterministically-derived *hardened* keys for ea=
ch use case under single standard, which should simplify future wallet impl=
ementations.
> And as I said, dedicated branches only help for the simple case. For exam=
ple, it doesn't address the more general problem of preventing reuse of key=
s in multiple distinct groups of multisig sets you participate in. If you w=
ant to solve that you need to keep track of index is for participating in =
what - and once you have something like that you don't need dedicated purpo=
se based derivation at all anymore.
In the BIP proposal there is a part on how multisigs can be created in a si=
mple and deterministic way without keys reuse.
> So I'm not sure I'd state it as us *needing* a dedicated purpose/branch f=
or single-key P2TR (and probably many other useful ways of using taproot ba=
sed spending policies...). But perhaps it's useful to have.
My proposal is to have a new purpose field supporting all the above: harden=
ed derivation that supports for multisigs, single-sigs etc.
Kind regards,
Maxim
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