Re: [TLS] Review comments on draft-rescorla-tls-opaque-prf-input-00.txt

Eric Rescorla <ekr@networkresonance.com> Thu, 18 January 2007 05:12 UTC

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Subject: Re: [TLS] Review comments on draft-rescorla-tls-opaque-prf-input-00.txt
References: <45AEA795.2080308@redhat.com> <BAY126-DAV192028B2EA5EB9D23929D892AA0@phx.gbl>
From: Eric Rescorla <ekr@networkresonance.com>
Date: Wed, 17 Jan 2007 21:12:24 -0800
In-Reply-To: <BAY126-DAV192028B2EA5EB9D23929D892AA0@phx.gbl> (home pw's message of "Wed, 17 Jan 2007 20:50:54 -0800")
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<home_pw@msn.com> writes:
> What is interesting now is the session resumption disclosure. This may
> explain why Eric is so adamant that he can FORCE a new handshake, so
> he can refresh the extensions values for a new TLS Connection?

Peter, it's generally polite not to attribute ulterior motives to
others. 


> But, as disclosed, its more confusing than before. Now the opaque PRF
> can only be used in pre-master-secret to master secret generation. In
> the other document and earlier in the paper, it seemed opaque PRF was
> being given a rationale for use in final KDF;'s generation of keying
> material.

First, I should state that I only have fairly limited insight into
the motivation for this extension. I was asked to help design
something with a particular set of parameters in the way that
would be most tasteful for TLS and that's what I did. I agree
it would be nice to have a more explicit rationale for these
parameters and I'm working on getting one.
         
That said, not re-mixing the new entropy into the KDF for 
session key generation wasn't an intentional design feature.
It's merely a limitation of the way that session resumption
and extensions interact.

-Ekr



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