From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 1CC62E85 for ; Fri, 21 Dec 2018 16:21:53 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from sender-of-o51.zoho.com (sender-of-o51.zoho.com [135.84.80.216]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 9D87583E for ; Fri, 21 Dec 2018 16:21:52 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; t=1545409310; cv=none; d=zoho.com; s=zohoarc; b=TsjddjaH+mzvOT3MtHUQeQWcnpITgOvqY0u2Za+n/9kSlyD30DnaeuDBOg2Y3dgxL2IaS+7InB7Up6zmtUR9e2hGsjyLDtLK5aBwZ2VurSm3MmI9COPkyQByTjim51U04LicicNIp7Sb05jdcc4lKVDakZ2q2Tinhh4+iNwXQmI= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1545409310; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:To:ARC-Authentication-Results; bh=fIj5zWzo0fft0Je5u3vQHI8Bb01YP8NDQ/0AW6N5fx8=; b=Q8prILr1+AWxSNtSBTKl7oA0HrQBL2uI9TQGho06+v7bBEojw0wTX4KrorU+StBYOwmmvnSGOu0m5O6imAVFAeuPR78pQJ018Ec+zx3gl85gQs8KW7guQS3TNZG5EoMlAF+jLC6BXCWk9WOUMApvJAhbpvTBNXlAdpVhNZEiAKg= ARC-Authentication-Results: i=1; mx.zoho.com; dkim=pass header.i=xbt.hk; spf=pass smtp.mailfrom=jl2012@xbt.hk; dmarc=pass header.from= header.from= Received: from [10.8.0.105] (n218103234118.netvigator.com [218.103.234.118]) by mx.zohomail.com with SMTPS id 1545409308634549.3261268469297; Fri, 21 Dec 2018 08:21:48 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 12.0 \(3445.100.39\)) From: Johnson Lau In-Reply-To: <87woo3uo4m.fsf@gmail.com> Date: Sat, 22 Dec 2018 00:21:42 +0800 Content-Transfer-Encoding: quoted-printable Message-Id: <96D7F9F7-4D1B-42ED-A82C-E714F3AED047@xbt.hk> References: <9F8C0789-48E9-448A-A239-DB4AFB902A00@xbt.hk> <87efadp3rl.fsf@gmail.com> <195B4583-CE97-4C3A-9582-3C0C013CC1E9@xbt.hk> <871s6cw1vt.fsf@gmail.com> <34A8F2C4-4732-4BE7-84F5-699B8D709D06@xbt.hk> <87woo3uo4m.fsf@gmail.com> To: Christian Decker X-Mailer: Apple Mail (2.3445.100.39) X-ZohoMailClient: External X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org X-Mailman-Approved-At: Fri, 21 Dec 2018 23:30:36 +0000 Cc: bitcoin-dev Subject: Re: [bitcoin-dev] Safer NOINPUT with output tagging X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 Dec 2018 16:21:53 -0000 > On 21 Dec 2018, at 7:15 PM, Christian Decker = wrote: >=20 > Johnson Lau writes: >=20 >> I think the use of OP_CSV (BIP112) is not needed here (although it >> doesn=E2=80=99t really harm except taking a few more bytes). All you = need is >> to sign the settlement tx with a BIP68 relative locktime. Since this >> is a 2-of-2 branch, both parties need to agree with the relative >> locktime, so it is not necessary to restrict it through OP_CSV >=20 > I keep forgetting about BIP68, but you're right, that should be > sufficient for our use-case and would safe us a few bytes. >=20 With taproot, this actually saves a lot more than a few bytes. For each = update, you will make 3 signatures. One is a SIGHASH_ALL spending the = setup TXO with no locktime. One is a NOINPUT spending a previous update = TXO with absolute locktime. One is a NOINPUT spending the latest update = TXO with relative locktime. For the first and third signatures, you will = just sign directly with the scriptPubKey, without revealing the hidden = taproot script. The second signature will reveal the taproot script, but = it is needed only when someone published an outdated update tx.