IETF Logo Mail Archive

Re: [openpgp] Fingerprints and their collisions resistance

Daniel Kahn Gillmor <dkg@fifthhorseman.net> Thu, 03 January 2013 23:08 UTC

Return-Path: <dkg@fifthhorseman.net>
X-Original-To: openpgp@ietfa.amsl.com
Delivered-To: openpgp@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id C03BC21F8D29 for <openpgp@ietfa.amsl.com>; Thu, 3 Jan 2013 15:08:51 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.599
X-Spam-Level:
X-Spam-Status: No, score=-2.599 tagged_above=-999 required=5 tests=[BAYES_00=-2.599]
Received: from mail.ietf.org ([64.170.98.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id JoMHm9ZtDOfk for <openpgp@ietfa.amsl.com>; Thu, 3 Jan 2013 15:08:50 -0800 (PST)
Received: from che.mayfirst.org (che.mayfirst.org [209.234.253.108]) by ietfa.amsl.com (Postfix) with ESMTP id 89DA321F8D12 for <openpgp@ietf.org>; Thu, 3 Jan 2013 15:08:50 -0800 (PST)
Received: from [192.168.13.194] (lair.fifthhorseman.net [108.58.6.98]) by che.mayfirst.org (Postfix) with ESMTPSA id A4742F970; Thu, 3 Jan 2013 18:08:45 -0500 (EST)
Message-ID: <50E60F7A.8000001@fifthhorseman.net>
Date: Thu, 03 Jan 2013 18:08:42 -0500
From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Icedove/17.0
MIME-Version: 1.0
To: Andrey Jivsov <openpgp@brainhub.org>
References: <50E530D6.6020609@brainhub.org> <50E5494E.6090905@iang.org> <50E60748.3040103@brainhub.org>
In-Reply-To: <50E60748.3040103@brainhub.org>
X-Enigmail-Version: 1.5
Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="----enig2IHEMGHKCJARCUKLRONKF"
Cc: openpgp@ietf.org
Subject: Re: [openpgp] Fingerprints and their collisions resistance
X-BeenThere: openpgp@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: "Ongoing discussion of OpenPGP issues." <openpgp.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/openpgp>, <mailto:openpgp-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/openpgp>
List-Post: <mailto:openpgp@ietf.org>
List-Help: <mailto:openpgp-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/openpgp>, <mailto:openpgp-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 03 Jan 2013 23:08:51 -0000

On 01/03/2013 05:33 PM, Andrey Jivsov wrote:
> In the process of writing such a draft I noticed that the only place in
> OpenPGP where SHA1 is used in collision resistance sensitive way without
> the possibility to change it is fingerprints.

As i mentioned on the discussion on the GnuPG discussion list, i remain
unconvinced that OpenPGP fingerprints need to be collision-resistant.
They certainly need to be able to resist preimage attacks, but i haven't
seen any convincing attacks that make me think collision resistance is
an issue.

Here's the recent GnuPG discussion:

 http://thread.gmane.org/gmane.comp.encryption.gpg.devel/17366/focus=17389

And here's earlier discussion from Daniel Nagy and myself on this list
suggesting that collision-resistance is an issue for fingerprints:

 http://thread.gmane.org/gmane.ietf.openpgp/6012/focus=6013
 http://thread.gmane.org/gmane.ietf.openpgp/7115/focus=7126

If anyone disagrees with this analysis, i would be interested in hearing
how failed collision-resistance of the fingerprint mechanism could lead
to practical attacks in OpenPGP.

> I have this Keccak in OpenPGP darft written, waiting to for the NIST to
> publish SHA-3 and the OIDs assigned.

thanks for doing this, i think this will be a useful contribution.

Regards,

	--dkg

v2.23.0 | Report a Bug | By Email