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=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 79FA0201B0 for ; Sun, 26 Feb 2017 01:14:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751890AbdBZBO1 (ORCPT ); Sat, 25 Feb 2017 20:14:27 -0500 Received: from outbound1.eu.mailhop.org ([52.28.251.132]:17258 "EHLO outbound1.eu.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751824AbdBZBO0 (ORCPT ); Sat, 25 Feb 2017 20:14:26 -0500 X-MHO-User: df46b5d5-fbc0-11e6-95b5-6dfd7dbb0ee5 X-Report-Abuse-To: https://support.duocircle.com/support/solutions/articles/5000540958-duocircle-standard-smtp-abuse-information X-Originating-IP: 173.50.81.193 X-Mail-Handler: DuoCircle Outbound SMTP Received: from io (unknown [173.50.81.193]) by outbound1.eu.mailhop.org (Halon) with ESMTPSA id df46b5d5-fbc0-11e6-95b5-6dfd7dbb0ee5; Sun, 26 Feb 2017 01:14:09 +0000 (UTC) Received: from io.lakedaemon.net (localhost [127.0.0.1]) by io (Postfix) with ESMTP id 2682C80018; Sun, 26 Feb 2017 01:13:59 +0000 (UTC) X-DKIM: OpenDKIM Filter v2.6.8 io 2682C80018 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lakedaemon.net; s=mail; t=1488071639; bh=fVfG0o+i9Dgl+ZJsmKy1Eh1d/kJiJBAofvUgBuMfaWg=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=gTgf30EFgPakK4m5iedBqlrOp7Iok4v9TpV4RCS4dHTn7KsQMGOzMoWJgpnW6cL+c 7LQ1CUnAZKOjkIT/V86lFXCgexH7h4jxN5P64hkUKr8TIUSxaatX5petwKpytKEJ5J MTrHS1knHIcINR0aH+SR/LYk5r8ttk/xqOYkiEQ/c4TA96eEFRglhUVfUSS1mJlVug dWrPXAk5BS1QGcrAr57KNekmdVwd2+HipGzHoSxbBtU5ykVbeAl9v8L+E2tUROuIZP hFzNlZmpAoT1Xgo5pLkBoP12iVBYr72gdsUciMd0UEBWWztwZzj3MWNIxMve5dCgQD nF7EbVVkIDyyw== Date: Sun, 26 Feb 2017 01:13:59 +0000 From: Jason Cooper To: Junio C Hamano Cc: Linus Torvalds , Jeff King , Ian Jackson , Joey Hess , Git Mailing List Subject: Re: SHA1 collisions found Message-ID: <20170226011359.GI11350@io.lakedaemon.net> References: <20170223164306.spg2avxzukkggrpb@kitenet.net> <22704.19873.860148.22472@chiark.greenend.org.uk> <20170224233929.p2yckbc6ksyox5nu@sigill.intra.peff.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Hi Junio, On Fri, Feb 24, 2017 at 10:10:01PM -0800, Junio C Hamano wrote: > I was thinking we would need mixed mode support for smoother > transition, but it now seems to me that the approach to stratify the > history into old and new is workable. As someone looking to deploy (and having previously deployed) git in unconventional roles, I'd like to add one caveat. The flag day in the history is great, but I'd like to be able to confirm the integrity of the old history. "Counter-hashing" the blobs is easy enough, but the trees, commits and tags would need to have, iiuc, some sort of cross-reference. As in my previous example, "git tag -v v3.16" also checks the counter hash to further verify the integrity of the history (yes, it *really* needs to check all of the old hashes, but I'd like to make sure I can do step one first). Would there be opposition to counter-hashing the old commits at the flag day? thx, Jason.