From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.2 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 4B4872013E for ; Fri, 3 Mar 2017 01:51:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751497AbdCCBvf (ORCPT ); Thu, 2 Mar 2017 20:51:35 -0500 Received: from ns332406.ip-37-187-123.eu ([37.187.123.207]:56314 "EHLO glandium.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751261AbdCCBva (ORCPT ); Thu, 2 Mar 2017 20:51:30 -0500 Received: from glandium by mitsuha.glandium.org with local (Exim 4.89_RC6) (envelope-from ) id 1cjcMp-0006LQ-QG; Fri, 03 Mar 2017 10:50:47 +0900 Date: Fri, 3 Mar 2017 10:50:47 +0900 From: Mike Hommey To: Linus Torvalds Cc: Joey Hess , Junio C Hamano , Jeff King , Ian Jackson , Git Mailing List Subject: Re: SHA1 collisions found Message-ID: <20170303015047.p4lpkdzp4hbpz5vi@glandium.org> References: <20170223164306.spg2avxzukkggrpb@kitenet.net> <22704.19873.860148.22472@chiark.greenend.org.uk> <20170224233929.p2yckbc6ksyox5nu@sigill.intra.peff.net> <20170302215457.l2zhxgnvhulw2hl5@kitenet.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-GPG-Fingerprint: 182E 161D 1130 B9FC CD7D B167 E42A A04F A6AA 8C72 User-Agent: NeoMutt/20170113 (1.7.2) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Thu, Mar 02, 2017 at 02:27:15PM -0800, Linus Torvalds wrote: > On Thu, Mar 2, 2017 at 1:54 PM, Joey Hess wrote: > > > > There's a surprising result of combining iterated hash functions, that > > the combination is no more difficult to attack than the strongest hash > > function used. > > Duh. I should actually have known that. I started reading the paper > and went "this seems very familiar". I'm pretty sure I've been pointed > at that paper before (or maybe just a similar one), and I just didn't > react enough for it to leave a lasting impact. What if the "object version" is a hash of the content (as opposed to header + content like the normal git hash)? Mike