Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1S54xs-0003qU-6B for bitcoin-development@lists.sourceforge.net; Wed, 07 Mar 2012 00:42:48 +0000 Received-SPF: pass (sog-mx-2.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.210.46 as permitted sender) client-ip=209.85.210.46; envelope-from=watsonbladd@gmail.com; helo=mail-pz0-f46.google.com; Received: from mail-pz0-f46.google.com ([209.85.210.46]) by sog-mx-2.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1S54xr-00042U-AN for bitcoin-development@lists.sourceforge.net; Wed, 07 Mar 2012 00:42:48 +0000 Received: by dajr28 with SMTP id r28so8606251daj.33 for ; Tue, 06 Mar 2012 16:42:41 -0800 (PST) MIME-Version: 1.0 Received: by 10.68.189.5 with SMTP id ge5mr914798pbc.50.1331080961195; Tue, 06 Mar 2012 16:42:41 -0800 (PST) Sender: watsonbladd@gmail.com Received: by 10.142.153.8 with HTTP; Tue, 6 Mar 2012 16:42:41 -0800 (PST) In-Reply-To: References: Date: Tue, 6 Mar 2012 18:42:41 -0600 X-Google-Sender-Auth: sDI1ECVN6Q-p38uR0D1g36r_znY Message-ID: From: Watson Ladd To: Gregory Maxwell Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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 (watsonbladd[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: 1S54xr-00042U-AN Cc: bitcoin-development@lists.sourceforge.net Subject: Re: [Bitcoin-development] Fwd: Proposal for a new opcode 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: Wed, 07 Mar 2012 00:42:48 -0000 On Tue, Mar 6, 2012 at 6:05 PM, Gregory Maxwell wrote: > On Fri, Mar 2, 2012 at 2:57 PM, Watson Ladd wrote: >> I am proposing a new opcode for the purposes of anonymous >> transactions. This new opcode enables scripts to be given proof that >> the receiver can carry out or has carried out a previous transaction. >> I'm currently working on a paper that discusses using this opcode for >> anonymous transactions. > > I believe I understand what the opcode does directly=E2=80=94 it just > validates an opaque signautre. I don't understand how it enables > anonymous transactions. > > Can you spell this out for me? One doesn't use this opcode as the sole thing to secure a transaction. Instead this opcode prevents double spend attacks against anonymization schemes. The idea is for Alice to give signatures to the recipients of funds, all signatures being equivalent. To avoid this from leading to a double-spend, we use a quorum method based on showing earlier redemptions happened. > > In particular I don't see why it is not, from the perspective of the > blockchain, isomorphic to a hash locked transaction. =C2=A0 (This > equivalence is more obvious when you think about how lamport > signtures turn simple hashing into a one time signature). Because you can't blind a lamport signature, it isn't. I'm searching for a place to post the current draft: it's not ready for anything official yet, but does seem to be of interest. Drop me a (offlist)line if you have ideas about where I can put it. Sincerely, Watson Ladd --=20 "Those who would give up Essential Liberty to purchase a little Temporary Safety deserve neither=C2=A0 Liberty nor Safety." -- Benjamin Franklin