From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David Symonds" Subject: Re: NIST's policy: sha-1 until 2010, after 2010 sha-2. Date: Sat, 29 Dec 2007 15:45:35 +1100 Message-ID: References: <998d0e4a0712282027y6e625141jcef90bd38fb83b75@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Linus Torvalds" , git@vger.kernel.org To: "J.C. Pizarro" X-From: git-owner@vger.kernel.org Sat Dec 29 05:46:04 2007 Return-path: Envelope-to: gcvg-git-2@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by lo.gmane.org with esmtp (Exim 4.50) id 1J8TaE-0000hh-NE for gcvg-git-2@gmane.org; Sat, 29 Dec 2007 05:46:03 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752599AbXL2Eph (ORCPT ); Fri, 28 Dec 2007 23:45:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753262AbXL2Eph (ORCPT ); Fri, 28 Dec 2007 23:45:37 -0500 Received: from rv-out-0910.google.com ([209.85.198.191]:46564 "EHLO rv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752323AbXL2Epg (ORCPT ); Fri, 28 Dec 2007 23:45:36 -0500 Received: by rv-out-0910.google.com with SMTP id k20so3689391rvb.1 for ; Fri, 28 Dec 2007 20:45:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; bh=Xb28iGlnpdpHvxPB3BHPk6ZCGC/ys4X7Tcwd7Cx22bo=; b=CigBQ12blbG5nA0A5ljGooUj5a92iiDYiRcGKGyo3M48uydiuHxyFqWSWSjnJNkbiRjg+aN9JYfhWw8WzC42D1os8e/QY8OsB+YJ+3L6id7GG7eoDxZdcTEl43/eT8d3ZfXhNkBSDPvmt6HMJJNtLDt2GCzqtTkX3xZWMurHWCw= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=OagPyDCv6z1ZT6EtfPXyHK28GFmbMZzShKQdLurLm/87ajmIkTQuk7gzHuaqaxUI7dln7qXSSqJEkClvRFEE9MQI8jissdPp/AzDhPWqFQeaBc4UaUxbk2P1/CSY/IyhnAw0PnAAyjO1TMSUQyClJaOAZ4lKvGeKUsb8DMceAKc= Received: by 10.141.87.13 with SMTP id p13mr5213584rvl.55.1198903535267; Fri, 28 Dec 2007 20:45:35 -0800 (PST) Received: by 10.141.115.4 with HTTP; Fri, 28 Dec 2007 20:45:35 -0800 (PST) In-Reply-To: <998d0e4a0712282027y6e625141jcef90bd38fb83b75@mail.gmail.com> Content-Disposition: inline Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On Dec 29, 2007 3:27 PM, J.C. Pizarro wrote: > Dear Linus Torvalds, > > What do you think to do when your git has to change from SHA-1 to SHA-2 > because of the weaker collision-resistance of SHA-1 in the next years? > > (e.g. from an damn developer trying to commit a collisioned-SHA-1 file) It's a non-issue. The closest-to-practical attack method on SHA-1 is a collision-finding attack, not a second pre-image attack, which means you can find two messages with the same hash. As far as I know, there's no significant weakness known for finding a pre-image, which would be the most practical way of weakening Git's "security" via SHA-1 substitution. Regardless, the use of SHA-1 in Git isn't primarily for security, though it is a nice side-effect. The SHA-1 is there for reliability in addressing and as a good hash. Dave.