Re: [TLS] draft-ietf-tls-cached-info-02 / New "Fast-Track" draft

Martin Rex <mrex@sap.com> Fri, 19 February 2010 16:13 UTC

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From: Martin Rex <mrex@sap.com>
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To: stefan@aaa-sec.com (Stefan Santesson)
Date: Fri, 19 Feb 2010 17:15:15 +0100 (MET)
In-Reply-To: <C7A467D8.8666%stefan@aaa-sec.com> from "Stefan Santesson" at Feb 19, 10 04:07:52 pm
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Cc: tls@ietf.org
Subject: Re: [TLS] draft-ietf-tls-cached-info-02 / New "Fast-Track" draft
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Stefan Santesson wrote:
> 
> On 10-02-19 3:03 PM, "Martin Rex" <mrex@sap.com>; wrote:
> 
> > I also think that reporting back in ServerHello for which elements
> > it supports caching would be a good idea.
> 
> I'm not opposing this.
> 
> Are you saying that the server (at server hello) should state which TYPE of
> elements is supports for caching, or do you propose that the server should
> state exactly which hash values received by the client the server accepts?
> 
> I thought you didn't want the server to be forced to choose which hash
> values it accepts at server hello time.


With "reporting back for which elements it supports caching"
I meant "supporting in theory", not an actual match of the
real data from future handshake messages with proposed hashed
values supplied by the client.

This should be done in a fashion that the client can probe
on the initial connect (i.e. when the client does not have any
values cached) to determine:

   - whether the server supports caching of data at all
   - for which elements the server supports caching in principle
   - confirmation which hash algorithm the server supports

which the client can then use to decide:
   - whether caching of any handshake data for that server makes
     any sense at all of would be a complete waste
   - which hash algorithm to use to identify cached handshake
     data in future handshakes with that server


-Martin