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Re: [TLS] Key Schedule (PRs #453, #454).

Ilari Liusvaara <ilariliusvaara@welho.com> Thu, 19 May 2016 19:35 UTC

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Date: Thu, 19 May 2016 22:35:18 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Eric Rescorla <ekr@rtfm.com>
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Subject: Re: [TLS] Key Schedule (PRs #453, #454).
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On Thu, May 19, 2016 at 12:13:45PM -0700, Eric Rescorla wrote:
> On Thu, May 19, 2016 at 12:11 PM, Ilari Liusvaara <ilariliusvaara@welho.com>
> wrote:
> 
> > On Thu, May 19, 2016 at 10:41:16AM -0700, Eric Rescorla wrote:
> >
> > Just one thing to be careful of: If one has off-handshake counter-
> > keys[1] (like the now-removed GDH 0-RTT mode had), one needs to hash
> > those in, or one gets all kinds of crypto screw (which may or may not
> > be actually exploitable...)
> >
> > The "context identifier" looks real handy for that purpose..
> 
> 
> Yep. We were thinking that too!
> 
> 
> Thanks for the quick look.

In very quick'n'dirty security analysis the other thing I noticed was
that if server handshake needs something to be nonce w.r.t. "SS", (e.g.
happens in GDHE-PSK-CERT modes MT posted I-D about), you need contexts
anyway, even with just "SS" being PSK.


-Ilari

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