Return-Path: <orlovsky@protonmail.com> Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id EB38FC000F for <bitcoin-dev@lists.linuxfoundation.org>; Thu, 18 Feb 2021 18:59:06 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id D248686985 for <bitcoin-dev@lists.linuxfoundation.org>; Thu, 18 Feb 2021 18:59:06 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id KAD_XMpUtZbf for <bitcoin-dev@lists.linuxfoundation.org>; Thu, 18 Feb 2021 18:59:04 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail2.protonmail.ch (mail2.protonmail.ch [185.70.40.22]) by fraxinus.osuosl.org (Postfix) with ESMTPS id D357D84EDB for <bitcoin-dev@lists.linuxfoundation.org>; Thu, 18 Feb 2021 18:59:03 +0000 (UTC) Date: Thu, 18 Feb 2021 18:58:54 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=protonmail; t=1613674741; bh=oh5ZK+6ehl7qDJYIvbdRL1Itces9Bub6d0oqAKjXYQI=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=qaExkz6ErMl9xWZjcj1i3FYz8YNQO+HQDaCsAHDr2NxkV9dWSDI6ihQSwmFAyfAlJ Rh94dIIsEs3hwlnsa32AWyF+6A4najJRwsxLV5Jii+UovYd7mvtXoJDCcZll2MRhCy glKmbp2g1Doc1DBKYN2LGq2KNOBqTiYqfJT7DMUc= To: Pieter Wuille <bitcoin-dev@wuille.net> From: Dr Maxim Orlovsky <orlovsky@protonmail.com> Reply-To: Dr Maxim Orlovsky <orlovsky@protonmail.com> Message-ID: <B51720B9-1BC4-4679-AA67-A1DE5687B89A@protonmail.com> In-Reply-To: <AzQAiClGFEDDux7hDtaD3As76nWOJELk9eck-_Ra4lDTwXQz2lYJEwRHjq9Gt65cA7AgKbidpNQlD-U6g5OKM-EaNvPbgva-ASzt-LcBDT8=@wuille.net> References: <D962F4E0-E10F-433D-BFC9-3462A8A9CF7A@protonmail.com> <mCGqNxZZgiKEO8gbRcHFUxcU5fGBMWMfkJdapM2Nuhe0gemmqXRfnyqqaRY70UFea1udvQe0LIYt9Ps3lsgDArVHlfeMOWacXqZ7ZiGzMTU=@wuille.net> <5096768E-3A77-4CD8-AC22-105CA63152A7@protonmail.com> <AzQAiClGFEDDux7hDtaD3As76nWOJELk9eck-_Ra4lDTwXQz2lYJEwRHjq9Gt65cA7AgKbidpNQlD-U6g5OKM-EaNvPbgva-ASzt-LcBDT8=@wuille.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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 X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion <bitcoin-dev.lists.linuxfoundation.org> List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/bitcoin-dev>, <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=unsubscribe> List-Archive: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/> List-Post: <mailto:bitcoin-dev@lists.linuxfoundation.org> List-Help: <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=help> List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>, <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=subscribe> X-List-Received-Date: Thu, 18 Feb 2021 18:59:07 -0000 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