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=-3.3 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD,T_DKIM_INVALID 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 233382022D for ; Thu, 23 Feb 2017 20:58:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751334AbdBWU6K (ORCPT ); Thu, 23 Feb 2017 15:58:10 -0500 Received: from kitenet.net ([66.228.36.95]:58986 "EHLO kitenet.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751277AbdBWU6I (ORCPT ); Thu, 23 Feb 2017 15:58:08 -0500 X-Question: 42 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=joeyh.name; s=mail; t=1487882826; bh=MIma7F8qViawKl7fA9csieLjOJ4g0L2YNUnHoO92vkI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=B+F1vzX2moyNLnj/+wgcECQZlXhgfOKv5e6AjWt7T/nuluWCLF92+5Wt3GymrojrA sGbNaFO6bpVuFBduBBXZ6oz/CtF4IwFzf2PxAPmWlGAKaajRBxL4vJPpCOFJIe2bMe BHXk1ni0DHhBYNBlm9qN90c1OqzKyqWOPUe8+whg= DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=joeyh.name; s=mail; t=1487882819; bh=MIma7F8qViawKl7fA9csieLjOJ4g0L2YNUnHoO92vkI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FUkBbqnNiyFZqViZ9fTPqfd3y/chmsV/Oyg1uKt1H7jfYOR6JmX/3QNn7fxz2lK6F /8wX5qJjjOM2xwK/saS7EbDMTfDEvrtI2uTRwHna23iW0ayL0vBaLEekeW51MpClV2 j/5VYClIXUpkjCa/MMUD4AZD1czZflcoWPBj5LEw= Date: Thu, 23 Feb 2017 16:46:59 -0400 From: Joey Hess To: Jeff King Cc: Git Mailing List Subject: Re: SHA1 collisions found Message-ID: <20170223204659.prmbuip4s4snwtci@kitenet.net> References: <20170223164306.spg2avxzukkggrpb@kitenet.net> <20170223173547.qljypk7sdqi37oha@kitenet.net> <20170223182147.hbsyxsmyijgkqu75@kitenet.net> <20170223184637.xr74k42vc6y2pmse@sigill.intra.peff.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="vwrg5avozjrh2i6s" Content-Disposition: inline In-Reply-To: <20170223184637.xr74k42vc6y2pmse@sigill.intra.peff.net> User-Agent: NeoMutt/20161126 (1.7.1) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org --vwrg5avozjrh2i6s Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Jeff King wrote: > It's not an identical prefix, but I think collision attacks generally > are along the lines of selecting two prefixes followed by garbage, and > then mutating the garbage on both sides. That would "work" in this case > (modulo the fact that git would complain about the NUL). >=20 > I haven't read the paper yet to see if that is the case here, though. The current attack is an identical-prefix attack, not chosen-prefix, so not quite to that point yet. The MD5 chosen-prefix attack was 2^15 harder than the known-prefix attack, but who knows if the numbers will be comprable for SHA1. > A related case is if you could stick a "cruft ...." header at the end of > the commit headers, and mutate its value (avoiding newlines). fsck > doesn't complain about that. git log and git show don't show such cruft headers either. BTW, the SHA attack only added ~128 bytes to the pdfs, not really a huge amount of garbage. --=20 see shy jo --vwrg5avozjrh2i6s Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEE6FpfY7MdJMHr8NgcyRDZIiUS48cFAlivSkMACgkQyRDZIiUS 48cLiQ/+JTSPSJK39BmC9qERSq0G21smBKzSjGzegptTGcdr/dspMWR8XnivpLO4 74QMYoGP96Uozm4DRJ7OloB3FmLJwj5HDAnvlsBuReD2ydmLhUc0eXEixf3u8UB7 8XIAzB5AVYpFjyebpd5Fu0NEjJndr3UwE7jMh1wC2eimE9yf86kt2Qi0QmXNchSZ AIoiOaqx7FO1OK7OX4HtKrkf4i4BjYLiw3o56E0xoFroP6lUT7+0MucmnTCXVsXa Hpy7rZo26JFENw+LetTUi4nv2W2Wsb80C8MWb513oG9odcF/gbLQMg92vMqv14eu KcunaW2waZoM1+a8GONmVyQGGh1Ikt35uvZ5/6Llo5RL14wGGBMVRIcU4vSKeX3+ Ueo9wD1wdPMNGi1Wglw9RFid2fZjO//oLSeCwI844cUdu84Wj9H17hvXW7nnoq2B k3EOKN1Wmtgs7qKL19woTSgWkzX68lQ28WFUMqUBgtM6KN2JsMOxYLp79cR6nIgx jNDQNzo9nxULL587urShCjHI5JVidxBT7h3r9Sf/V3yUrOgiwNGny1PhM4GoSslg BnTyNCjMWEuJdqRrJEsdtKPlbYh/s23G16saIJHLyC9mlUeeSO4K6TcTmQp5aY2+ 9tWKXxwqBTlBXBLtHzrvdTq9KbWB7qkPT43ZGBGf388rKLHtXHs= =Lpr8 -----END PGP SIGNATURE----- --vwrg5avozjrh2i6s--