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Re: [TLS] Zero-RTT Data & PSK

Martin Thomson <martin.thomson@gmail.com> Sat, 10 September 2016 10:35 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Sat, 10 Sep 2016 20:35:44 +1000
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To: Hannes Tschofenig <hannes.tschofenig@gmx.net>
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Subject: Re: [TLS] Zero-RTT Data & PSK
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On 9 September 2016 at 23:37, Hannes Tschofenig
<hannes.tschofenig@gmx.net> wrote:
> I am wondering why I cannot use Zero-RTT with just PSK-based authentication
> (without a prior ticket change).

I think that you would need to bind more things to the key in that
case, but I assume that it would be OK if you did so.  You already
need to pair a PSK with a hash, but if you paired it with a whole
cipher suite instead and also the ALPN (which could be null), then I
see no reason not to permit 0-RTT for pure PSK.  (I think that cipher
suite + ALPN is sufficient, but someone can correct me if I missed
anything.)

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