From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1WG8I5-0003rU-8n for bitcoin-development@lists.sourceforge.net; Wed, 19 Feb 2014 14:38:25 +0000 Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.213.182 as permitted sender) client-ip=209.85.213.182; envelope-from=pieter.wuille@gmail.com; helo=mail-ig0-f182.google.com; Received: from mail-ig0-f182.google.com ([209.85.213.182]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1WG8I4-0007T9-Ht for bitcoin-development@lists.sourceforge.net; Wed, 19 Feb 2014 14:38:25 +0000 Received: by mail-ig0-f182.google.com with SMTP id uy17so1320086igb.3 for ; Wed, 19 Feb 2014 06:38:19 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.50.60.103 with SMTP id g7mr1613331igr.20.1392820699087; Wed, 19 Feb 2014 06:38:19 -0800 (PST) Received: by 10.50.100.10 with HTTP; Wed, 19 Feb 2014 06:38:19 -0800 (PST) In-Reply-To: References: <52FBD948.906@monetize.io> <201402122252.31060.luke@dashjr.org> Date: Wed, 19 Feb 2014 15:38:19 +0100 Message-ID: From: Pieter Wuille To: Michael Gronager Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Spam-Score: -1.6 (-) 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 (pieter.wuille[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 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: 1WG8I4-0007T9-Ht Cc: Bitcoin Development Subject: Re: [Bitcoin-development] [RFC] [BIP proposal] Dealing with malleability 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, 19 Feb 2014 14:38:25 -0000 On Wed, Feb 19, 2014 at 3:11 PM, Michael Gronager wrote: > Why introduce a new transaction version for this purpose ? Wouldn't it be= more elegant to simply let: > > 1. the next bitcoin version "prettify" all relayed transactions as determ= inistic transactions fulfilling the scheme 1-6 effectively blocking any mal= leability attack? If miners would upgrade then all transactions in blocks w= ould have a deterministic hash. I consider actively mutating other's transactions worse than not relaying them. If we want people to make their software deal with malleability, either will work. Regarding deterministic hash: that's impossible. Some signature hash types are inherently (and intentionally) malleable. I don't think we should pretend to want to change that. The purpose is making non-malleability a choice the sender of a transaction can make. Most of the rules actually are enforced by IsStandard already now. Only #1 and #7 aren't. #1 affects the majority of all transactions, so changing it right now would be painful. #7 only affects multisig. > 2. In a version later one could block relay of non deterministic transact= ions, as well as the acceptance of blocks with non-confirming transactions. > > To non-standard conforming clients this "prettify" change of hash would b= e seen as a constant malleability attack, but given the "prettify" code it = is to fix any client into producing only conforming transactions, just by r= unning the transaction through it before broadcast. > > There is a possible fork risk in step 2. above - if a majority of miners = still havn't upgraded to 1 when 2 is introduced. We could monitor % non con= forming transaction in a block and only introduce 2. once that number is su= fficiently small for a certain duration - criteria: > * Switch on forcing of unmalleable transactions in blocks when there has = been only conforming transactions for 1000 blocks. The problem in making these rules into consensus rule (affecting tx/block validity) is that some rules (in particular #3) may not be wanted by everyone, as they effectively limit the possibilities of the script language further. As it is ultimately only about protecting senders who care about non-malleability, introducing a new transaction version is a very neat way of accomplishing that. The new block version number is only there to coordinate the rollout, and choosing an automatic forking point. --=20 Pieter