IETF Logo Mail Archive

[openpgp] WWhy or why not SHA{2,3}-512 (was: SHA3 algorithm ids)

Werner Koch <wk@gnupg.org> Tue, 11 August 2015 15:50 UTC

Return-Path: <wk@gnupg.org>
X-Original-To: openpgp@ietfa.amsl.com
Delivered-To: openpgp@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id C3C3E1A1A56 for <openpgp@ietfa.amsl.com>; Tue, 11 Aug 2015 08:50:35 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Level:
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9] autolearn=ham
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 PKeS1WP2FAXe for <openpgp@ietfa.amsl.com>; Tue, 11 Aug 2015 08:50:34 -0700 (PDT)
Received: from kerckhoffs.g10code.com (kerckhoffs.g10code.com [IPv6:2001:aa8:fff1:100::22]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id A1A581A1A20 for <openpgp@ietf.org>; Tue, 11 Aug 2015 08:50:34 -0700 (PDT)
Received: from uucp by kerckhoffs.g10code.com with local-rmail (Exim 4.80 #2 (Debian)) id 1ZPBou-0001hl-VP for <openpgp@ietf.org>; Tue, 11 Aug 2015 17:50:33 +0200
Received: from wk by vigenere.g10code.de with local (Exim 4.84 #3 (Debian)) id 1ZPBmM-00028k-Fw; Tue, 11 Aug 2015 17:47:54 +0200
From: Werner Koch <wk@gnupg.org>
To: Peter Gutmann <pgut001@cs.auckland.ac.nz>
References: <87y4hmi19i.fsf@vigenere.g10code.de> <7540C7A9-2830-4A63-8310-B684796DA279@nohats.ca> <55C681FC.9010100@iang.org> <sjma8tztbgo.fsf@securerf.ihtfp.org> <CAMm+Lwj7SxXTn+KD-eQSeZHwJB36tCgD1t0bodVsp3ovOaZ8mw@mail.gmail.com> <9A043F3CF02CD34C8E74AC1594475C73F4AD7C72@uxcn10-5.UoA.auckland.ac.nz>
Organisation: g10 Code GmbH
X-message-flag: Mails containing HTML will not be read! Please send only plain text.
OpenPGP: id=F2AD85AC1E42B367; url=finger:wk@g10code.com
Mail-Followup-To: Peter Gutmann <pgut001@cs.auckland.ac.nz>, Phillip Hallam-Baker <phill@hallambaker.com>, Derek Atkins <derek@ihtfp.com>, IETF OpenPGP <openpgp@ietf.org>, ianG <iang@iang.org>
Date: Tue, 11 Aug 2015 17:47:54 +0200
In-Reply-To: <9A043F3CF02CD34C8E74AC1594475C73F4AD7C72@uxcn10-5.UoA.auckland.ac.nz> (Peter Gutmann's message of "Tue, 11 Aug 2015 13:21:07 +0000")
Message-ID: <87614lg72t.fsf_-_@vigenere.g10code.de>
User-Agent: Gnus/5.13 (Gnus v5.13)
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Archived-At: <http://mailarchive.ietf.org/arch/msg/openpgp/niMUC20ORtPx48esBoSwjom3x1U>
Cc: Phillip Hallam-Baker <phill@hallambaker.com>, Derek Atkins <derek@ihtfp.com>, ianG <iang@iang.org>, IETF OpenPGP <openpgp@ietf.org>
Subject: [openpgp] WWhy or why not SHA{2,3}-512 (was: SHA3 algorithm ids)
X-BeenThere: openpgp@ietf.org
X-Mailman-Version: 2.1.15
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: Tue, 11 Aug 2015 15:50:35 -0000

On Tue, 11 Aug 2015 15:21, pgut001@cs.auckland.ac.nz said:

> What's the clear need for -512?  By which I mean a demonstrated practical need
> for a hash size of 64 bytes, not a hypothesised need given an imaginary
> attack.  I can see a need for SHA-256 (to replace SHA-1), but for something
> like SHA3-512 all I can see are downsides (compared to SHA2-256).

One advantage of SHA-512 (SHA2) is that it faster than SHA-256 on modern
machines.  Thus SHA-512 truncated to 256 might be an option.  This would
eventually allow to write a small application which uses SHA-512 as its
only hash algorithm.


Salam-Shalom,

   Werner


-- 
Die Gedanken sind frei.  Ausnahmen regelt ein Bundesgesetz.

v2.23.0 | Report a Bug | By Email