From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 6E5291F597 for ; Sun, 22 Jul 2018 10:10:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728224AbeGVLGS (ORCPT ); Sun, 22 Jul 2018 07:06:18 -0400 Received: from goldorak5.eric.deplagne.name ([213.246.56.18]:58745 "EHLO exim4.goldorak5.eric.deplagne.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728175AbeGVLGS (ORCPT ); Sun, 22 Jul 2018 07:06:18 -0400 X-Greylist: delayed 2127 seconds by postgrey-1.27 at vger.kernel.org; Sun, 22 Jul 2018 07:06:17 EDT Received: from [192.168.0.4] (helo=mail.eric.deplagne.name) by exim4.goldorak5.eric.deplagne.name with esmtp (Exim 4.72) (envelope-from ) id 1fhAlG-00066k-Pt; Sun, 22 Jul 2018 11:34:42 +0200 Received: from deplagne by mail.eric.deplagne.name with local (Exim 4.69) (envelope-from ) id 1fhAlG-00066e-Ot; Sun, 22 Jul 2018 11:34:42 +0200 Date: Sun, 22 Jul 2018 11:34:42 +0200 From: Eric Deplagne To: "brian m. carlson" , Johannes Schindelin , Jonathan Nieder , git@vger.kernel.org, demerphq , Linus Torvalds , Adam Langley , The Keccak Team Subject: Re: Hash algorithm analysis Message-ID: <20180722093442.GK11431@mail.eric.deplagne.name> References: <20180609205628.GB38834@genre.crustytoothpaste.net> <20180609224913.GC38834@genre.crustytoothpaste.net> <20180611192942.GC20665@aiede.svl.corp.google.com> <20180720215220.GB18502@genre.crustytoothpaste.net> <20180721235941.GG18502@genre.crustytoothpaste.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="FU8v9NgvNgS/pFcX" Content-Disposition: inline In-Reply-To: <20180721235941.GG18502@genre.crustytoothpaste.net> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org --FU8v9NgvNgS/pFcX Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, 21 Jul 2018 23:59:41 +0000, brian m. carlson wrote: > On Sun, Jul 22, 2018 at 12:38:41AM +0200, Johannes Schindelin wrote: > > Do you really want to value contributors' opinion more than > > cryptographers'? I mean, that's exactly what got us into this hard-coded > > SHA-1 mess in the first place. >=20 > I agree (believe me, of all people, I agree) that hard-coding SHA-1 was > a bad choice in retrospect. But I've solicited contributors' opinions > because the Git Project needs to make a decision *for this project* > about the algorithm we're going to use going forward. >=20 > > And to set the record straight: I do not have a strong preference of the > > hash algorithm. But cryprographers I have the incredible luck to have > > access to, by virtue of being a colleague, did mention their preference. >=20 > I don't know your colleagues, and they haven't commented here. One > person that has commented here is Adam Langley. It is my impression > (and anyone is free to correct me if I'm incorrect) that he is indeed a > cryptographer. To quote him[0]: >=20 > I think this group can safely assume that SHA-256, SHA-512, BLAKE2, > K12, etc are all secure to the extent that I don't believe that making > comparisons between them on that axis is meaningful. Thus I think the > question is primarily concerned with performance and implementation > availability. >=20 > [=E2=80=A6] >=20 > So, overall, none of these choices should obviously be excluded. The > considerations at this point are not cryptographic and the tradeoff > between implementation ease and performance is one that the git > community would have to make. Am I completely out of the game, or the statement that "the considerations at this point are not cryptographic" is just the wrongest ? I mean, if that was true, would we not be sticking to SHA1 ? > I'm aware that cryptographers tend to prefer algorithms that have been > studied longer over ones that have been studied less. They also prefer > algorithms built in the open to ones developed behind closed doors. >=20 > SHA-256 has the benefit that it has been studied for a long time, but it > was also designed in secret by the NSA. SHA3-256 was created with > significant study in the open, but is not as mature. BLAKE2b has been > incorporated into standards like Argon2, but has been weakened slightly > for performance. >=20 > I'm not sure that there's a really obvious choice here. >=20 > I'm at the point where to continue the work that I'm doing, I need to > make a decision. I'm happy to follow the consensus if there is one, but > it does not appear that there is. >=20 > I will admit that I don't love making this decision by myself, because > right now, whatever I pick, somebody is going to be unhappy. I want to > state, unambiguously, that I'm trying to make a decision that is in the > interests of the Git Project, the community, and our users. >=20 > I'm happy to wait a few more days to see if a consensus develops; if so, > I'll follow it. If we haven't come to one by, say, Wednesday, I'll make > a decision and write my patches accordingly. The community is free, as > always, to reject my patches if taking them is not in the interest of > the project. >=20 > [0] https://public-inbox.org/git/CAL9PXLzhPyE+geUdcLmd=3DpidT5P8eFEBbSgX_= dS88knz2q_LSw@mail.gmail.com/ > --=20 > brian m. carlson: Houston, Texas, US > OpenPGP: https://keybase.io/bk2204 --=20 Eric Deplagne --FU8v9NgvNgS/pFcX Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iD8DBQFbVE+yej7DisjVpq4RAoBJAJ4xHSa7h3zs3nJh2/rZ45H9xnLFngCdH3Es mPpXZ4qGnEeSxuxL5iVfD0c= =YnxW -----END PGP SIGNATURE----- --FU8v9NgvNgS/pFcX--