IETF Logo Mail Archive

Re: [openpgp] "SHA-1 is a Shambles" and forging PGP WoT signatures

Damien Goutte-Gattat <dgouttegattat@incenp.org> Fri, 24 January 2020 21:21 UTC

Return-Path: <dgouttegattat@incenp.org>
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 558B61200A4 for <openpgp@ietfa.amsl.com>; Fri, 24 Jan 2020 13:21:35 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.001
X-Spam-Level:
X-Spam-Status: No, score=-2.001 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=incenp.org
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OMvWpTkGIPnU for <openpgp@ietfa.amsl.com>; Fri, 24 Jan 2020 13:21:32 -0800 (PST)
Received: from mail.incenp.org (mail.incenp.org [51.254.143.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 6ACFE120052 for <openpgp@ietf.org>; Fri, 24 Jan 2020 13:21:32 -0800 (PST)
Received: from localhost (dgouttegattat.plus.com [81.174.245.146]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.incenp.org (Postfix) with ESMTPSA id C515D20168; Fri, 24 Jan 2020 22:21:28 +0100 (CET)
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=incenp.org; s=201912; t=1579900889; bh=AmlBJAWbF3A0Q66Jj+omMx8391qKt4fTzdBiuGdiqtw=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=AyHT5jZV9p143O3DVidJ2EKf8rQvrg/HQSUvaI6RJfxtl/IE0slH+jTdDZRJBtdZH ePArPa2JSD8NqcC+MzcR+U/f2jM54NLIiqV8cApKvSCq+4S7v1FlrJMdQsFNrSBIzC T37piHBQo5ZkKZiKREgRy8fJAIVudswjDygvcT/0=
Date: Fri, 24 Jan 2020 21:21:28 +0000
From: Damien Goutte-Gattat <dgouttegattat@incenp.org>
To: Michael Richardson <mcr@sandelman.ca>
Cc: openpgp@ietf.org
Message-ID: <20200124212128.vxqr6nq7kvdnfjkh@dynein.local.incenp.org>
OpenPGP: id=4FA2082362FE73AD03B88830A8DC7067E25FBABB; url=https://incenp.org/srv/dgouttegattat.asc; preference=signencrypt
References: <d8321b24-8836-2702-6b01-242b4cab932f@rub.de> <e4dc8c25-2282-17a8-7e64-cee55f43be84@kuix.de> <20200124002228.ek7bcwlbghuoborr@dynein.local.incenp.org> <24969.1579885029@localhost>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="an5kmzd6rom4r7dy"
Content-Disposition: inline
In-Reply-To: <24969.1579885029@localhost>
Archived-At: <https://mailarchive.ietf.org/arch/msg/openpgp/yL8Z5vED5AKRROu3aQaq3elb07c>
Subject: Re: [openpgp] "SHA-1 is a Shambles" and forging PGP WoT signatures
X-BeenThere: openpgp@ietf.org
X-Mailman-Version: 2.1.29
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: <https://mailarchive.ietf.org/arch/browse/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: Fri, 24 Jan 2020 21:21:35 -0000

On Fri, Jan 24, 2020 at 11:57:09AM -0500, Michael Richardson wrote:
>I guess, maybe if the key is big enough (rsa 8K, bigger), that the 
>bytes could be in the prime itself.  Are you saying that?

Yes.


> If so, I wonder what the smallest key for which this is true is.

The collision found by the authors used 9 near-collision blocks (4608 
bits). They believe it would have been possible to find a collision with 
7 near-collision blocks (3584 bits), which could fit into a 4096-bit RSA 
key.


- Damien

v2.23.0 | Report a Bug | By Email