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 0C677DF2 for ; Fri, 23 Sep 2016 22:35:09 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from zinan.dashjr.org (unknown [192.3.11.21]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 872881F6 for ; Fri, 23 Sep 2016 22:35:08 +0000 (UTC) Received: from ishibashi.localnet (unknown [IPv6:2001:470:5:265:61b6:56a6:b03d:28d6]) (Authenticated sender: luke-jr) by zinan.dashjr.org (Postfix) with ESMTPSA id E2F7538AB81A; Fri, 23 Sep 2016 22:34:44 +0000 (UTC) X-Hashcash: 1:25:160923:bitcoin-dev@lists.linuxfoundation.org::mPx2JHxAgNQIIVzP:aUsOx X-Hashcash: 1:25:160923:tomz@freedommail.ch::X=2jxHNZ1kYk2Fdu:a/UgC From: Luke Dashjr To: bitcoin-dev@lists.linuxfoundation.org, Tom Date: Fri, 23 Sep 2016 22:34:41 +0000 User-Agent: KMail/1.13.7 (Linux/4.4.21-gentoo; KDE/4.14.24; x86_64; ; ) References: <201609230957.03138.luke@dashjr.org> <2403444.9CSRyRIcH2@garp> In-Reply-To: <2403444.9CSRyRIcH2@garp> X-PGP-Key-Fingerprint: E463 A93F 5F31 17EE DE6C 7316 BD02 9424 21F4 889F X-PGP-Key-ID: BD02942421F4889F X-PGP-Keyserver: hkp://pgp.mit.edu MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201609232234.43689.luke@dashjr.org> X-Spam-Status: No, score=-0.9 required=5.0 tests=BAYES_00,RDNS_DYNAMIC autolearn=no version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Subject: Re: [bitcoin-dev] BIP draft: OP_CHECKBLOCKATHEIGHT 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, 23 Sep 2016 22:35:09 -0000 Joe sends Alice 5 BTC (UTXO 0). Fred sends Alice 4 BTC (UTXO 1). Alice sends Bob 4 BTC using UTXO 1 (creating UTXO 2). Fred double-spends UTXO 1 with UTXO 1-B. This invalidates Alice's transfer to Bob. Alice has UTXO 0 which she can send to Bob (UTXO 3), but if she does so, it is possible that UTXO 0 could be mined, and then both UTXO 2 and UTXO 3 which would result in her giving Bob a total of 8 BTC rather than merely 4 BTC. Even if Alice waits until Fred's UTXO 1-B confirms 10 blocks deep, it is not impossible for a reorganization to reverse those 10 blocks and confirm UTXO 1 again. Using OP_CHECKBLOCKATHEIGHT, however, Alice can create UTXO 3 such that it is valid only in the blockchain where Fred's UTXO 1-B has confirmed. This way, if that block is reorganized out, UTXO 3 is invalid, and either Bob receives only the original UTXO 2, or Alice can create a UTXO 3-B which is valid in the reorganized blockchain if it again confirms the UTXO 1-B double-spend. Luke On Friday, September 23, 2016 2:37:39 PM Tom via bitcoin-dev wrote: > On Friday 23 Sep 2016 09:57:01 Luke Dashjr via bitcoin-dev wrote: > > This BIP describes a new opcode (OP_CHECKBLOCKATHEIGHT) for the Bitcoin > > scripting system to address reissuing bitcoin transactions when the coins > > they spend have been conflicted/double-spent. > > > > https://github.com/luke-jr/bips/blob/bip-cbah/bip-cbah.mediawiki > > Can you walk us through a real live usecase which this solves? I read it > and I think I understand it, but I can't see the attack every giving the > attacker any benefit (or the attacked losing anything). > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev