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

Martin Rex <mrex@sap.com> Fri, 19 February 2010 17:57 UTC

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From: Martin Rex <mrex@sap.com>
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To: brian@briansmith.org (Brian Smith)
Date: Fri, 19 Feb 2010 18:58:59 +0100 (MET)
In-Reply-To: <4B7D811D.50909@briansmith.org> from "Brian Smith" at Feb 18, 10 12:04:13 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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Brian Smith wrote:
> 
> Stefan Santesson wrote:
> > Well,
> >
> > I went through my change list and have now updated and reposted the draft as
> > draft-03.
> >
> > Changes can be viewed from:
> > http://tools.ietf.org/rfcdiff?url2=draft-ietf-tls-cached-info-03.txt
>    
> I think it is especially important to have the SHA-1 requirement 
> changed. It is a big hassle to require SHA-1 for compliance when now 
> every use of SHA-1 has to be reviewed. Also, mandating SHA-1 would be in 
> conflict with other requirements--especially requirements to follow NIST 
> and NSA recommendations regarding algorithms. At a minimum, make SHA-1 
> support mandatory only if/when the connection's negotiated version is 
> less than TLS 1.2.

Another issue that you may not have realized is what the requirement
to support SHA-1 really means.  

http://tools.ietf.org/html/rfc3365#section-7

The requirement for SHA-1 is for the purpose of interoperability,
and it makes perfect sense to require SHA-1 to be present in
implementations so that this can be implemented for all existing
protocol stacks, including those prior to TLSv1.2.

Adding a "RECOMMENDED to support SHA-256" to the document wouldn't hurt.

The question which algorithm consumers of this technology
will use (and which algorithms they reject) is a seperate
question.


The protocol version {0x03,0x00}, {0x03,0x01} and {0x03,0x02}
are going to be around for quite some years to come.

-Martin