Re: [TLS] AAED ciphers: AES-GCM vs AES-EAX/AES-CCM: a meta-analysis

Michael Clark <michael@metaparadigm.com> Thu, 25 December 2014 01:01 UTC

Return-Path: <michael@metaparadigm.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 375571A6F53 for <tls@ietfa.amsl.com>; Wed, 24 Dec 2014 17:01:45 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.468
X-Spam-Level:
X-Spam-Status: No, score=-1.468 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, IP_NOT_FRIENDLY=0.334, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_DKIM_INVALID=0.01, T_RP_MATCHES_RCVD=-0.01] autolearn=no
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 U6-rMKLHoFct for <tls@ietfa.amsl.com>; Wed, 24 Dec 2014 17:01:43 -0800 (PST)
Received: from klaatu.metaparadigm.com (klaatu.metaparadigm.com [67.207.128.90]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id A4D991A6F51 for <tls@ietf.org>; Wed, 24 Dec 2014 17:01:43 -0800 (PST)
Received: from monty.local (unknown.maxonline.com.sg [58.182.90.50] (may be forged)) (authenticated bits=0) by klaatu.metaparadigm.com (8.14.4/8.14.4/Debian-4) with ESMTP id sBP1MaIZ012376 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT); Thu, 25 Dec 2014 01:22:40 GMT
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=metaparadigm.com; s=klaatu; t=1419470563; bh=IaUTLejvQIUAjuluZU3Y/KWt5znJEGB84bBk1rPr6yc=; h=Date:From:To:Subject:References:In-Reply-To:From; b=cgDpyDDBLbZ+DamWT571c9I2U4cj3QWGMlcdsBsnP9ZlkksPnMEBc57abQmTYPlj1 23Ws/dxaySqK8yM5NJGL0B7TiwLQO6HtSKzSNZpgsFAoM66OwUd09rfgDQr5DA8ctF gLQqFsP67sqsjuVWilwEjLeRKubaX3h6fUWZBHzQ=
Message-ID: <549B61E4.8080301@metaparadigm.com>
Date: Thu, 25 Dec 2014 09:01:24 +0800
From: Michael Clark <michael@metaparadigm.com>
Organization: Metaparadigm Pte Ltd
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.3.0
MIME-Version: 1.0
To: Peter Gutmann <pgut001@cs.auckland.ac.nz>, "<tls@ietf.org>" <tls@ietf.org>
References: <9A043F3CF02CD34C8E74AC1594475C73AAF49636@uxcn10-tdc05.UoA.auckland.ac.nz>
In-Reply-To: <9A043F3CF02CD34C8E74AC1594475C73AAF49636@uxcn10-tdc05.UoA.auckland.ac.nz>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 8bit
X-Virus-Scanned: clamav-milter 0.98.4 at klaatu.metaparadigm.com
X-Virus-Status: Clean
Archived-At: http://mailarchive.ietf.org/arch/msg/tls/83AyfI1THxBGPhG2_hLr633EVmE
Subject: Re: [TLS] AAED ciphers: AES-GCM vs AES-EAX/AES-CCM: a meta-analysis
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." <tls.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/tls>, <mailto:tls-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/tls/>
List-Post: <mailto:tls@ietf.org>
List-Help: <mailto:tls-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/tls>, <mailto:tls-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 25 Dec 2014 01:01:45 -0000

Hi Peter,

Someone pointed out RFC 7366 to me off list. I will read. I like the
idea of encrypt-then-MAC being a core requirement for TLSv1.3.

Before I've read through can we do this with it?

AES-256-GCM + hmac_null   = 128 bits authentication
AES-256-CBC + hmac_sha128 = 128 bits authentication

AES-256-GCM + hmac_sha128 = 256 bits authentication
AES-256-CBC + hmac_sha256 = 256 bits authentication

AES-256-GCM + hmac_sha256 = 384 bits authentication
AES-256-CBC + hmac_sha384 = 384 bits authentication

I like the idea of >= 256 bits authentication, and the idea of the
combination of a cipher based MAC and PRF based MAC for AES-GCM, given
the properties of the AES-GCM CTR mode 'variant' and GHASH GF(2^128).

Michael.


On 24/12/14 2:15 pm, Peter Gutmann wrote:
> Michael Clark <michael@metaparadigm.com>; writes:
> 
>> I have been doing some independent research on TLS AEAD ciphers and decided
>> to share a meta-analysis on AES-GCM versus AES-EAX/AES-CCM
> 
> If you're going to look at these, what about also looking at encrypt-then-MAC,
> which is another AEAD mechanism?
> 
> Peter.
> 
> _______________________________________________
> TLS mailing list
> TLS@ietf.org
> https://www.ietf.org/mailman/listinfo/tls
>