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=-3.5 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 EB0E2201B0 for ; Sat, 25 Feb 2017 18:51:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751861AbdBYSvA (ORCPT ); Sat, 25 Feb 2017 13:51:00 -0500 Received: from castro.crustytoothpaste.net ([75.10.60.170]:40918 "EHLO castro.crustytoothpaste.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751695AbdBYSu7 (ORCPT ); Sat, 25 Feb 2017 13:50:59 -0500 Received: from genre.crustytoothpaste.net (unknown [IPv6:2001:470:b978:101:f8da:200e:3546:3090]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by castro.crustytoothpaste.net (Postfix) with ESMTPSA id A2386280AD; Sat, 25 Feb 2017 18:50:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=crustytoothpaste.net; s=default; t=1488048656; bh=irq2AyALS2V+abofTL96L+EUWv+TRbMkptBLgnfgJqo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dp5G7pvN+2W1KTQBc54hqlF93+RlDW4SI501LlQDgI0NdDIhgKiK1zaMCT3RjC105 zwK9VKI3K+2Sdh+z2/iCvHl9ilLM2IpmLhhdUBCnTD5HCEdvJ0AlBTz2E0GXuqaRGL lz7SSRFQjBbyW93t5f4JVNkTNfAQv4sRbXYQ+6EpZXFqt5GfKQqxNBf4FDtwD82BnV GYGBGrslehrrHTij0HTa45TifO32U9WzBXN62sdBA7goUq/GH/WpL0syH1uHkjKfPk IWmQBFPOVXLBMe4+j5RRKRW5EVpRcemQ/UuHMRAeCMMVwamOp2lMA9gestbdvB1CHi UOBHTxy3cexOHCS2H4oA9jY2UYmuapFuMqmoqlsHeHkW3oOsvSjeso0OJ6fIU1wa+2 +OCd5LYW6fkiuVW1oS7KbFyEUkG77yOqF/paYBhNhnkiL95fV4lWeXM9JlFlh1EEic L7pAhJkuUc2EQiaXE4YLC4OrYQzknesK79dwQCf91w7yvM7PU2b Date: Sat, 25 Feb 2017 18:50:50 +0000 From: "brian m. carlson" To: Junio C Hamano Cc: Ian Jackson , Joey Hess , git@vger.kernel.org Subject: Re: SHA1 collisions found Message-ID: <20170225185050.t6e5txrppofgelsf@genre.crustytoothpaste.net> Mail-Followup-To: "brian m. carlson" , Junio C Hamano , Ian Jackson , Joey Hess , git@vger.kernel.org References: <20170223164306.spg2avxzukkggrpb@kitenet.net> <22704.19873.860148.22472@chiark.greenend.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="rg4ykdx3gehd6zye" Content-Disposition: inline In-Reply-To: X-Machine: Running on genre using GNU/Linux on x86_64 (Linux kernel 4.9.0-2-amd64) User-Agent: NeoMutt/20170113 (1.7.2) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org --rg4ykdx3gehd6zye Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Feb 24, 2017 at 09:32:13AM -0800, Junio C Hamano wrote: > Ian Jackson writes: >=20 > > I have been thinking about how to do a transition from SHA1 to another > > hash function. >=20 > Good. I think many of us have also been, too, not necessarily just > in the past few days in response to shattered, but over the last 10 > years, yet without coming to a consensus design ;-) >=20 > > I have concluded that: > > > > * We can should avoid expecting everyone to rewrite all their > > history. >=20 > Yes. There are security implications for old objects if we mix hashes, but I suppose people who want better security will just rewrite history anyway. > As long as the reader can tell from the format of object names > stored in the "new object format" object from what era is being > referred to in some way [*1*], we can name new objects with only new > hash, I would think. "new refers only to new" that stratifies > objects into older and newer may make things simpler, but I am not > convinced yet that it would give our users a smooth enough > transition path (but I am open to be educated and pursuaded the > other way). I would simply use multihash[0] for this purpose. New-style objects serialize data in multihash format, so it's immediately obvious what hash we're referring to. That makes future transitions less problematic. [0] https://github.com/multiformats/multihash --=20 brian m. carlson / brian with sandals: Houston, Texas, US +1 832 623 2791 | https://www.crustytoothpaste.net/~bmc | My opinion only OpenPGP: https://keybase.io/bk2204 --rg4ykdx3gehd6zye Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.1.18 (GNU/Linux) iQIzBAABCgAdFiEEX8OngXdrJt+H9ww3v1NdgR9S9osFAlix0goACgkQv1NdgR9S 9ouOMxAAh7kO7ymkmFEe3NLyS+YWApYEzmvbefsEMLMv+5CcX5bPtRsfuE7bOC+9 ZBfBwq5QomlRVaM5TydURUS5hdVnEQdKlRoaknIs0IAl7mL3Z4RkatWpQVMRkHtM OmHQuXgCIFUQ7tR6apYZZk5o/wVKKFm47lXXeSsT/TXaSWHB2QbTYYnY5G3m6FzD xLUACzRHTezmt2qlwmakB9mtEeOKtMpQvTSljVjp69z5/i8HnqBS62xI1bsbnCiG wTy713xaHFo5TNqrcur1KZGZFWsFQ2xBjx3fRnJWfntqitE1YieKJ4OwIk7PGS8u 9pactLL0OBl1k9DqOicamjJccWK7rjAoB1h74N057aDvG/urkdkcLXyzcDosmewK ibNWELrR/psJiprgn/KNSLPAZN2mHpACyUrs09+siFhVBlcP37rCn1+Z42caKTrY rDlFtFiu6vSehLpgsh7ouG6I728nheNUBxASLJZih4qGJRAn8m1gUHnNiUfvBlvD fAy6yJI7CJV1ZmFyE+r3jKgnDGDfVjjVcbbVzZYqQr/GkZ+YsqTErtCYFUIwKsS1 l+TB7jGVUvtfRuXsDZCQZe+nr3EYEKRBPHQvQ/tlqSVLC62+yGkwSnW3rbkGx9+P nl0y7L/fvTkR1q4H/WrxoXpC/2RcVFJMzDeEuy0+2phgnRhucyE= =nVCj -----END PGP SIGNATURE----- --rg4ykdx3gehd6zye--