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 2723172A for ; Thu, 17 Nov 2016 08:44:11 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from outmail149082.authsmtp.co.uk (outmail149082.authsmtp.co.uk [62.13.149.82]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 453DA148 for ; Thu, 17 Nov 2016 08:44:09 +0000 (UTC) Received: from mail-c232.authsmtp.com (mail-c232.authsmtp.com [62.13.128.232]) by punt20.authsmtp.com (8.14.2/8.14.2/) with ESMTP id uAH8i8iJ088833; Thu, 17 Nov 2016 08:44:08 GMT Received: from petertodd.org (ec2-52-5-185-120.compute-1.amazonaws.com [52.5.185.120]) (authenticated bits=0) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id uAH8i6XU004649 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 17 Nov 2016 08:44:07 GMT Received: from [127.0.0.1] (localhost [127.0.0.1]) by petertodd.org (Postfix) with ESMTPSA id 387F2400F7; Thu, 17 Nov 2016 08:39:25 +0000 (UTC) Received: by localhost (Postfix, from userid 1000) id 597A42047A; Thu, 17 Nov 2016 03:44:05 -0500 (EST) Date: Thu, 17 Nov 2016 03:44:05 -0500 From: Peter Todd To: Eric Voskuil , Bitcoin Protocol Discussion Message-ID: <20161117084405.GA12334@savin.petertodd.org> References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="lrZ03NoBR/3+SXJZ" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Server-Quench: 009dccfe-aca2-11e6-829e-00151795d556 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aQdMdwUUFloCAgsB AmAbW1xeVFl7WWQ7 bghPaBtcak9QXgdq T0pMXVMcUXQQCUUH bnseUh10cwwIeX54 bUIsXnBSCBcpIxNg Ex0FF3AHZDJmdWgd WRVFdwNVdQJNdxoR b1V5GhFYa3VsNCMk FAgyOXU9MCtqYA50 elpVZVsUTQ4hPwZn G1gDGykiB0QOWyQ0 KVRmNVcHVHwcYA0B G3oZOxogKRgKDRZX G3QFKjJDJlQNDwYm FQddTEsTFiFGAE8D X-Authentic-SMTP: 61633532353630.1037:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 52.5.185.120/25 X-AuthVirus-Status: No virus detected - but ensure you scan with your own anti-virus system. X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Subject: Re: [bitcoin-dev] BIP30 and BIP34 interaction (was Re: [BIP Proposal] Buried Deployments) 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: Thu, 17 Nov 2016 08:44:11 -0000 --lrZ03NoBR/3+SXJZ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Nov 16, 2016 at 04:43:08PM -0800, Eric Voskuil via bitcoin-dev wrot= e: > > This means that all future transactions will have different txids... > rules do guarantee it. >=20 > No, it means that the chance is small, there is a difference. >=20 > If there is an address collision, someone may lose some money. If there > is a tx hash collision, and implementations handle this differently, it > will produce a chain split. As such this is not something that a node > can just dismiss. If they do they are implementing a hard fork. If there is a tx hash collision it is almost certainly going to be because SHA256 has become weak through advances in cryptography, much like MD5. If = that is the case, Bitcoin is fundementally broken because the blockchain no long= er can be relied upon to commit to a unique transaction history: miners would = be able to generate blocks that have SHA256 collisions in transactions and even the merkle tree itself, making it possible to simultaneously mine two (or m= ore) contradictory transaction histories at once. Meanwhile the probability of SHA256 _not_ being broken and a collision being found is low enough that we should be more worried about earth-killing asteroids and mutant sharks, among other things. Quoting Bruce Schneier: These numbers have nothing to do with the technology of the devices; th= ey are the maximums that thermodynamics will allow. And they strongly imply th= at brute-force attacks against 256-bit keys will be infeasible until compu= ters are built from something other than matter and occupy something other than = space. -https://www.schneier.com/blog/archives/2009/09/the_doghouse_cr.html --=20 https://petertodd.org 'peter'[:-1]@petertodd.org --lrZ03NoBR/3+SXJZ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iQEcBAEBCgAGBQJYLW3RAAoJECSBQD2l8JH7M7cH/jdRWlfcDAL11/CsB1Q1YcKo /cSxhrxGSZSj6ITsjzUAqnYa5ONhyOQKC/LDixPhrBMAA1yFbvHWjrAKVC0WFMuX WFpBYySQtTugRyzAEJs3tGKR/MCsXHqYEmeAxWCE8sd7B7SJC9crXWy3ljXvzirB 2emswZtPJQk1SClUa12uODw/FzdxpB64zmlSg3AH3/rds8NvcqdqI4gm9Qh0ZgNO QbRsoZo5b9ZbPRjyx7lurq7y6MGTrtaIvLWtCPFL0mRpTB8KsnHcrHvQiW8/TAIy 4b34FLGUWyxVmKMfEaC0iC0whIvV+z3w2JqmqAFWISKSbCKMX5jSp9PfMxCt3LI= =DL6K -----END PGP SIGNATURE----- --lrZ03NoBR/3+SXJZ--