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 887688DC for ; Thu, 17 Nov 2016 11:22:04 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-pg0-f47.google.com (mail-pg0-f47.google.com [74.125.83.47]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id E1DF9309 for ; Thu, 17 Nov 2016 11:22:03 +0000 (UTC) Received: by mail-pg0-f47.google.com with SMTP id 3so90943506pgd.0 for ; Thu, 17 Nov 2016 03:22:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=voskuil-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to; bh=pPofu3vxC/caTcjzFw3dt7ZVgljg5WvjpKxc6HoQWmE=; b=ZwTyR8w+rX7Zk9IDrTZOV2vmGau6SMinOZW1PKe5M6SVsouJ52xxOeAUiylXLbHWlm Hq3P377uxpSxjD+zqxyQDcQg7szg3rg4h4TLe1UwfSF6hnrxmgmd85JO12TSHeGJ0y4T J8DhHFQeHqE0gv/lIeVJ0ZoPhaoJWKBCUx/+uuQoz6t9+l7DCG/LnKftAsNmK+bo/7Zo CTjJWt/D3DHEUl2SG6CPvXMwi44MTwNwNpfag7sucDhTak0kMoeJS7SncDP6MRgrK5zf 8lufxmFyOxZONsVIqWMALLXu6eopMy5C6opPyhOmqCbRvR3VFZATdE8p/M90NcOJKT79 OiyA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to; bh=pPofu3vxC/caTcjzFw3dt7ZVgljg5WvjpKxc6HoQWmE=; b=WdKHWL2FZrcfKmUIOkk+6vrP/irGCeQ+kbT45+4v07n5lkv6kdVOe9aKDRMyOdqcdp SRmjQs+KZmlSgWkvBClLsjhbGdyfG/AoEHnIEr1bJaqeNO6tNwhNmlCMy1wmyDhIruww CV1vNiWGpmtsI6t3Nyv90LM4AEllZSweH3YbDVrnSA6B5eHG/iSyq6jhCrxUxAGmpEqH TQBbNuqY+B5PpSmho8UrhPV0y4P3vO1YJd1QOKPVx4qq+JYirQKP9eXpUXsjsuTg0bAW yuuPwHveyb/DmILhgXqLpSJoK3Gaow+PdCb65h9x4iM6rrg2tIvyCMBk2wGMIj834YFF G14g== X-Gm-Message-State: ABUngvdJM9Kyysu4Sd2JVQtcWEwxCIE8OmBCx9B7RWsg/c/Xxx2OzHPetJ9rof5n6ayYnQ== X-Received: by 10.98.90.132 with SMTP id o126mr4021688pfb.41.1479381723164; Thu, 17 Nov 2016 03:22:03 -0800 (PST) Received: from ?IPv6:2601:600:9000:d69e:8084:4206:2529:776d? ([2601:600:9000:d69e:8084:4206:2529:776d]) by smtp.gmail.com with ESMTPSA id b64sm6426909pfc.74.2016.11.17.03.22.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 17 Nov 2016 03:22:02 -0800 (PST) To: bitcoin-dev@lists.linuxfoundation.org References: From: Eric Voskuil X-Enigmail-Draft-Status: N0110 Message-ID: <5ef23296-5909-a350-ab11-e717f8fffc41@voskuil.org> Date: Thu, 17 Nov 2016 03:22:03 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="DtpSSIt28nqorWbD08hVUPGlwLuDDgmtH" X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org X-Mailman-Approved-At: Thu, 17 Nov 2016 11:22:42 +0000 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 11:22:04 -0000 This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --DtpSSIt28nqorWbD08hVUPGlwLuDDgmtH Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 11/17/2016 02:22 AM, Tier Nolan via bitcoin-dev wrote: > On Thu, Nov 17, 2016 at 12:43 AM, Eric Voskuil > wrote: >=20 > > This means that all future transactions will have different txids= =2E.. > rules do guarantee it. >=20 > No, it means that the chance is small, there is a difference. >=20 > I think we are mostly in agreement then? It is just terminology. Sure, if you accept that mostly is not fully - just as unlikely is not impossible. > In terms of discussing the BIP, barring a hash collision, it does make > duplicate txids impossible. That's like saying, as long as we exclude car accidents from consideration, car accidents are impossible. > Given that a hash collision is so unlikely, the qualifier should be > added to those making claims that require hash collisions rather than > those who assume that they aren't possible. >=20 > You could have said "However nothing precludes different txs from havin= g > the same hash, but it requires a hash collision". I generally try to avoid speaking in tautologies :) > Thinking about it, a re-org to before the enforcement height could allo= w > it. The checkpoints protect against that though. > =20 > As such this is not something that a node > can just dismiss.=20 >=20 > The security of many parts of the system is based on hash collisions no= t > being possible. This is not the case. Block hash duplicates within the same chain are invalid as a matter of consensus, which is the opposite of assuming impossibility. Tx hash collisions are explicitly allowed in the case that preceding tx with the same hash is unspent. This is also not a reliance on the impossibility of hash collision. Core certainly implements this distincti= on: https://github.com/bitcoin/bitcoin/blob/master/src/main.cpp#L2419-L2426 Address hashes and script hashes can collide without harming the security of Bitcoin (although address owner(s) may experience harm). Rare in this case is sufficient because of this distinction. Compact blocks contemplates hash collisions: https://github.com/bitcoin/bips/blob/master/bip-0152.mediawiki#Random_col= lision_probabilty Checkpoints aren't part of Bitcoin security, so even the remote possibility of two different potential blocks, with the same hash, at the same height in the same chain, does not indicate a problem. There is no case where the security of Bitcoin assumes that hashes never collide. Consensus rules have specific handling for both block hash collisions and tx hash collisions. e --DtpSSIt28nqorWbD08hVUPGlwLuDDgmtH Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQEcBAEBAgAGBQJYLZLbAAoJEDzYwH8LXOFOFTQIAIdcDnwiwfv+5jFhwr6ZUU8J 2gSZTlVCO7p7RYwqBrvB3oEm6N7Mxspn751SLzIea22LoPEL2OqJRB2l/rYwGJ1k lQ2eyInXt8CQICj0Dfa9p6zJnPzIGbauz4z462gc+XGceJv36sShrE3X5ZS61b5F W2vSC6jNBz3OlRg3KocCyhNaUDxDqWslE7iMdRzFNTCTsxWu3bc0ioblCsjvmmJo Xeb0+5kitMQK/jh0BvT2Tt1/0B9Ymeq9QeDg8sSaK9Cyw15ZEBmCPLIdYnumB7V3 Jw8eo92FaXtHaaSwhRYIOn/MqrkIgsy4/+zk52LddXz+2pvsyvLRR+rCKhVCfJA= =zb3u -----END PGP SIGNATURE----- --DtpSSIt28nqorWbD08hVUPGlwLuDDgmtH--