From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Y2dKa-0002RS-Pr for bitcoin-development@lists.sourceforge.net; Sun, 21 Dec 2014 10:01:44 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.192.48 as permitted sender) client-ip=209.85.192.48; envelope-from=adam.back@gmail.com; helo=mail-qg0-f48.google.com; Received: from mail-qg0-f48.google.com ([209.85.192.48]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1Y2dKZ-0001L1-3F for bitcoin-development@lists.sourceforge.net; Sun, 21 Dec 2014 10:01:44 +0000 Received: by mail-qg0-f48.google.com with SMTP id f51so2359924qge.35 for ; Sun, 21 Dec 2014 02:01:37 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.224.25.79 with SMTP id y15mr28244923qab.78.1419156097622; Sun, 21 Dec 2014 02:01:37 -0800 (PST) Sender: adam.back@gmail.com Received: by 10.96.189.10 with HTTP; Sun, 21 Dec 2014 02:01:37 -0800 (PST) In-Reply-To: <20141220144800.GA26284@savin.petertodd.org> References: <20141212090551.GA8259@muck> <20141220144800.GA26284@savin.petertodd.org> Date: Sun, 21 Dec 2014 10:01:37 +0000 X-Google-Sender-Auth: pfSW7YdZ7mf_2JxD_-vTWIpVmJY Message-ID: From: Adam Back To: Peter Todd Content-Type: text/plain; charset=UTF-8 X-Spam-Score: -1.5 (-) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (adam.back[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1Y2dKZ-0001L1-3F Cc: Bitcoin Dev Subject: Re: [Bitcoin-development] The relationship between Proof-of-Publication and Anti-Replay Oracles X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 21 Dec 2014 10:01:44 -0000 On 20 December 2014 at 14:48, Peter Todd wrote: > We need the following primitives operating on message m, pubkey p, and a > valid signature sig1 for m, p: > > AntiReplaySign(m, p, sig1) -> sig2 > VerifyAntiReplaySig(m, p, sig2) -> True or False > > Additionally once AntiReplaySign() has been used once for a given pubkey > it is impossible to re-run the primitive on a different message m'. This > is of course impossible to implement with math alone, but we can > implement it with a trusted third party. Well while you cant prevent it you could render it insecure enabling miners to take funds. That could work via a one-show signature; normal ECDSA being address a=H(Q), public key Q=dG, R=kG, r=R.x, s=(H(m)+rd)/k, signature (r,s), verify: a=?H(Q) and sR=?H(m)G+rQ one-show being: a=H(Q,R), verify being: a=?H(Q,R) and sR=?H(m)G+rQ. Now that is unsafe to double-spend by design as only that specific R is usable and as we know reusing R with different messages leaks the private key because: s=(H(m)+rd)/k and s'=(H(m')+rd)/k implies sk=H(m)+rd and s'k=H(m')+rd so k=(H(m)-H(m'))/(s'-s), and d=(sk-H(m))/r. Adam