IETF Logo Mail Archive

Re: [core] Chairs' review of draft-ietf-core-stateless-03.txt

Carsten Bormann <cabo@tzi.org> Fri, 01 November 2019 06:44 UTC

Return-Path: <cabo@tzi.org>
X-Original-To: core@ietfa.amsl.com
Delivered-To: core@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 30EEE120059 for <core@ietfa.amsl.com>; Thu, 31 Oct 2019 23:44:21 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -4.199
X-Spam-Level:
X-Spam-Status: No, score=-4.199 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=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 mTtKtToTTMm3 for <core@ietfa.amsl.com>; Thu, 31 Oct 2019 23:44:17 -0700 (PDT)
Received: from gabriel-vm-2.zfn.uni-bremen.de (gabriel-vm-2.zfn.uni-bremen.de [134.102.50.17]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 7A15D12001E for <core@ietf.org>; Thu, 31 Oct 2019 23:44:17 -0700 (PDT)
Received: from client-0150.vpn.uni-bremen.de (client-0150.vpn.uni-bremen.de [134.102.107.150]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by gabriel-vm-2.zfn.uni-bremen.de (Postfix) with ESMTPSA id 474CMz5fllzywP; Fri, 1 Nov 2019 07:44:15 +0100 (CET)
Content-Type: text/plain; charset="utf-8"
Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\))
From: Carsten Bormann <cabo@tzi.org>
In-Reply-To: <27A826D9-5F28-4044-BE61-E7CD1C05EA90@arm.com>
Date: Fri, 01 Nov 2019 07:44:15 +0100
Cc: Core WG mailing list <core@ietf.org>
X-Mao-Original-Outgoing-Id: 594283453.793837-a02085aa838ecf724b63d1f1c2738c08
Content-Transfer-Encoding: quoted-printable
Message-Id: <781AE8D3-761F-461E-A727-C918391E158D@tzi.org>
References: <157237477119.11043.4363082013315464920@ietfa.amsl.com> <F964F5EF-96F7-49EC-BECB-0604B16F31FF@tzi.org> <27A826D9-5F28-4044-BE61-E7CD1C05EA90@arm.com>
To: Thomas Fossati <Thomas.Fossati@arm.com>
X-Mailer: Apple Mail (2.3445.9.1)
Archived-At: <https://mailarchive.ietf.org/arch/msg/core/R3KochRd-NBYI1bQ34pFdC-iBnU>
Subject: Re: [core] Chairs' review of draft-ietf-core-stateless-03.txt
X-BeenThere: core@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Constrained RESTful Environments \(CoRE\) Working Group list" <core.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/core>, <mailto:core-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/core/>
List-Post: <mailto:core@ietf.org>
List-Help: <mailto:core-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/core>, <mailto:core-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 01 Nov 2019 06:44:21 -0000

Hi Thomas,

thank you again for all your great input on this draft.

> On Oct 31, 2019, at 23:19, Thomas Fossati <Thomas.Fossati@arm.com> wrote:
> 
> On 31/10/2019, 17:08, "core on behalf of Carsten Bormann" <core-bounces@ietf.org on behalf of cabo@tzi.org> wrote:
>> 
>>   When using AES-CCM, repeated use of the same nonce under the same
>>   key
>> 
>> Not just AES-CCM, just about any AEAD.
> 
> The problem is not with AEAD per se, we could have picked GCM-SIV and
> there would have been no trouble.  The problem is with the underlying
> CTR.

Right, that’s why my proposed text specifically talks about “encryption mode that depends on a nonce”.

> Quibbles aside, the document recommends CCM -- over other AEAD
> constructions -- and does so consciously, I think, to provide the best
> trade-off between overall security, wire efficiency and processing cost.
> 
> This point does not surface in the current text, but the recommendation
> for CCM is actually quite precise, and maybe worth an upper-case
> RECOMMENDED?

I agree that this is a good recommendation.  It is not an interoperability requirement, though (and 64 bits of authenticator may actually be a bit low for some applications), so the purist in me isn’t thrilled about using a BCP 14 keyword.

Grüße, Carsten

v2.23.0 | Report a Bug | By Email