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=-5.2 required=3.0 tests=AWL,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 06B1D20195 for ; Fri, 22 Jul 2016 15:59:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751845AbcGVP7t (ORCPT ); Fri, 22 Jul 2016 11:59:49 -0400 Received: from pb-smtp2.pobox.com ([64.147.108.71]:60114 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751244AbcGVP7s (ORCPT ); Fri, 22 Jul 2016 11:59:48 -0400 Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 927252CBD8; Fri, 22 Jul 2016 11:59:46 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; s=sasl; bh=uAJtonZpAHSqEZ0DaqoLQfQg6R4=; b=BEC5ue oOgRUeL5te3Wr/sy+rM6vWYvsVFhxRnHNKDH7SayTdBfQ/1wKhfafWZybZRq4eYd e3ymDXXwKBLzCGsifdKFFmzILsVEA1tlw5CpriU46nW+D1xFtFVb7TZBMdyFKdeZ mrGIJkoOGza+xXvVr0P4+mXfrS8Hd6XBh0Iwo= DomainKey-Signature: a=rsa-sha1; c=nofws; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; q=dns; s=sasl; b=rqlwc+w5Yu66MwirCBdUx555CULPds+r C9D3upvvZq7f1wztjn50uD/iL+B8TBEuiBiexjHFq4cx3EEtMslAyx/ru40ZVOyk HSye5NgwKS8T2i60GUAORuTD8vVRDGwJqn5V5TpA+tElyXy4DevNEDgCwtHJBA+p SSOEjbGShlc= Received: from pb-smtp2.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 8B7492CBD7; Fri, 22 Jul 2016 11:59:46 -0400 (EDT) Received: from pobox.com (unknown [104.132.0.95]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by pb-smtp2.pobox.com (Postfix) with ESMTPSA id 137622CBD6; Fri, 22 Jul 2016 11:59:46 -0400 (EDT) From: Junio C Hamano To: Johannes Schindelin Cc: "brian m. carlson" , Theodore Ts'o , Duy Nguyen , Herczeg Zsolt , Git Mailing List Subject: Re: Git and SHA-1 security (again) References: <20160716201313.GA298717@vauxhall.crustytoothpaste.net> <20160717142157.GA6644@vauxhall.crustytoothpaste.net> <20160717154234.GC6644@vauxhall.crustytoothpaste.net> <20160717162349.GB11276@thunk.org> <20160717220417.GE6644@vauxhall.crustytoothpaste.net> Date: Fri, 22 Jul 2016 08:59:42 -0700 In-Reply-To: (Johannes Schindelin's message of "Thu, 21 Jul 2016 14:53:33 +0200 (CEST)") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Pobox-Relay-ID: 4FA4168E-5025-11E6-8FC6-EE617A1B28F4-77302942!pb-smtp2.pobox.com Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Johannes Schindelin writes: > Hi Junio, > > On Mon, 18 Jul 2016, Junio C Hamano wrote: > >> "brian m. carlson" writes: >> >> > I will say that the pack format will likely require some changes, >> > because it assumes ... The reason is that we can't have an >> > unambiguous parse of the current objects if two hash algorithms are in >> > use.... So when we look at a new hash, we need to provide an >> > unambiguous way to know what hash is in use. The two choices are to >> > either require all object use the new hash, or to extend the objects >> > to include the hash. Until a couple days ago, I had planned to do the >> > former. I had not even considered using a multihash approach due to >> > the complexity. >> >> Objects in Git identify themselves, but once you introduce the second >> hash function (as opposed to replacing the hash function to a new one), >> you would allow people to call the same object by two names. That has >> interesting implications. >> >> [...] > > So essentially you are saying that the multi-hash approach has too many > negative implications, right? At least that is what I understand. > > Looks more and more like we do need to convert repositories wholesale, and > keep a two-way mapping for talking to remote repositories. > > Would you concur? Not necessarily. That was me thinking aloud, listing some issues that I would imagine to be tricky to solve, without even attempting to be exhaustive, that I expect to see solved in a good end-result implementation. For example, "I do not see a nice way to solve X myself without doing Y" in the message you are responding to does not necessarily mean there is no good solution to X (just "I do not think of any offhand"), and it does not mean I think it is terrible that we have to do Y to solve X.