Re: [TLS] Safe ECC usage

mrex@sap.com (Martin Rex) Mon, 30 September 2013 22:50 UTC

Return-Path: <mrex@sap.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id AB39421F8D12 for <tls@ietfa.amsl.com>; Mon, 30 Sep 2013 15:50:38 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -10.184
X-Spam-Level:
X-Spam-Status: No, score=-10.184 tagged_above=-999 required=5 tests=[AWL=0.065, BAYES_00=-2.599, HELO_EQ_DE=0.35, RCVD_IN_DNSWL_HI=-8]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id tBpxvUwF6r4d for <tls@ietfa.amsl.com>; Mon, 30 Sep 2013 15:50:33 -0700 (PDT)
Received: from smtpde01.sap-ag.de (smtpde01.sap-ag.de [155.56.68.170]) by ietfa.amsl.com (Postfix) with ESMTP id D9C7321F8F09 for <tls@ietf.org>; Mon, 30 Sep 2013 15:50:29 -0700 (PDT)
Received: from mail05.wdf.sap.corp by smtpde01.sap-ag.de (26) with ESMTP id r8UMoQXk026048 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Tue, 1 Oct 2013 00:50:26 +0200 (MEST)
In-Reply-To: <CAPMEXDb4=BzU5JwnAFJRjdXHEa30Ara8VMbi2hZGneuKA3s0iw@mail.gmail.com>
To: Kyle Hamilton <aerowolf@gmail.com>
Date: Tue, 1 Oct 2013 00:50:26 +0200 (CEST)
X-Mailer: ELM [version 2.4ME+ PL125 (25)]
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset="US-ASCII"
Message-Id: <20130930225026.5DBF11A9C3@ld9781.wdf.sap.corp>
From: mrex@sap.com (Martin Rex)
X-SAP: out
Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Safe ECC usage
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
Reply-To: mrex@sap.com
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: Mon, 30 Sep 2013 22:50:49 -0000

Kyle Hamilton wrote:
> 
> That's all well and good, but perhaps should you try to figure out how your
> functions can in fact be used in such standards as TLS without having to
> resort to pulling hens' teeth?
> 
> Or perhaps apply your (admittedly much better than mine) intellect to
> figure out how to create a single public key from a single private key
> which can be used for both signing and key derivation, thus permitting
> consolidation of both into a single X.509 Certificate structure?  The lack
> of this is in fact a major impediment to using self-signed certificates as
> containers for curve25519 public keys.

I currently do not see any benefit from using EC for digital signatures,
but instead a huge amount of code, complexity and IPR issues (did you
look at the CertiCom idea how to charge?).

What I believe would be more attractive is an alternative to rfc4492
for ECDHE_RSA based on curve25519 (and _just_ curve25519), i.e.
a small number of new cipher suites and an additional ClientKeyExchange
and ServerKeyExchange variant specifically tailord for curve25519, so
that there are real benefits to a full-blown and generic rfc4492 TLS EC
crypto.

-Martin