Re: [TLS] Issue 49: Finished.verify length

Eric Rescorla <ekr@networkresonance.com> Fri, 14 September 2007 18:40 UTC

Return-path: <tls-bounces@lists.ietf.org>
Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com) by megatron.ietf.org with esmtp (Exim 4.43) id 1IWG5L-00080N-Vs; Fri, 14 Sep 2007 14:40:11 -0400
Received: from [10.91.34.44] (helo=ietf-mx.ietf.org) by megatron.ietf.org with esmtp (Exim 4.43) id 1IWG5K-00080F-Uq for tls@ietf.org; Fri, 14 Sep 2007 14:40:10 -0400
Received: from [209.213.211.195] (helo=delta.rtfm.com) by ietf-mx.ietf.org with esmtp (Exim 4.43) id 1IWG5J-0006ee-Mh for tls@ietf.org; Fri, 14 Sep 2007 14:40:10 -0400
Received: from delta.rtfm.com (localhost.rtfm.com [127.0.0.1]) by delta.rtfm.com (Postfix) with ESMTP id 6B09F33C21; Fri, 14 Sep 2007 11:36:33 -0700 (PDT)
Date: Fri, 14 Sep 2007 11:36:32 -0700
From: Eric Rescorla <ekr@networkresonance.com>
To: Pasi.Eronen@nokia.com
Subject: Re: [TLS] Issue 49: Finished.verify length
In-Reply-To: <B356D8F434D20B40A8CEDAEC305A1F2404966D3F@esebe105.NOE.Nokia.com>
References: <20070914090853.GA20702@tau.invalid> <B356D8F434D20B40A8CEDAEC305A1F2404937712@esebe105.NOE.Nokia.com> <20070914120310.GA29073@tau.invalid> <B356D8F434D20B40A8CEDAEC305A1F2404937802@esebe105.NOE.Nokia.com> <20070914141809.2439533C21@delta.rtfm.com> <B356D8F434D20B40A8CEDAEC305A1F2404966D3F@esebe105.NOE.Nokia.com>
User-Agent: Wanderlust/2.14.0 (Africa) Emacs/21.3 Mule/5.0 (SAKAKI)
MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka")
Content-Type: text/plain; charset="US-ASCII"
Message-Id: <20070914183633.6B09F33C21@delta.rtfm.com>
X-Spam-Score: 0.1 (/)
X-Scan-Signature: e5ba305d0e64821bf3d8bc5d3bb07228
Cc: tls@ietf.org
X-BeenThere: tls@lists.ietf.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." <tls.lists.ietf.org>
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/tls>, <mailto:tls-request@lists.ietf.org?subject=unsubscribe>
List-Archive: <http://www1.ietf.org/pipermail/tls>
List-Post: <mailto:tls@lists.ietf.org>
List-Help: <mailto:tls-request@lists.ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/tls>, <mailto:tls-request@lists.ietf.org?subject=subscribe>
Errors-To: tls-bounces@lists.ietf.org

At Fri, 14 Sep 2007 17:28:24 +0300,
<Pasi.Eronen@nokia.com> wrote:
> 
> Eric Rescorla wrote:
> 
> > I'm still trying to understand the rationale for why it makes sense
> > to have a verify_data != 12 bytes. Pasi, could you elaborate?
> 
> Again, I'm not suggesting changing it from 12 bytes; just allowing
> the agility to change it in the future without new TLS version.
> 
> One (somewhat hypothetical) use would be a cipher suite that tries 
> to have _everything_ at 256-bit security level (maybe for some 
> government approval reasons; not today, but maybe 5 years from now).
> 
> You might argue that this kind of security level isn't really
> needed, but then again, some people seem to be willing to go
> to great lengths to match these "security levels" (just think
> of SHA-224.. :-)

OK, I see where you're going with this, but I'm not sure it requires
us to do anything now. If we're confronted with such a cipher suite,
we can just have the document Update TLS 1.2, since it would only
be applicable to that new cipher suite. I don't think this needs
a version revision.

Unless you're proposing making this a variable length vector, whcih
seems like a bad idea, since it should be defined in the cipher
suite.
				   
-Ekr

_______________________________________________
TLS mailing list
TLS@lists.ietf.org
https://www1.ietf.org/mailman/listinfo/tls