Re: [TLS] 0-RTT (Was: Re: 0-RTT and Anti-Replay)

Ilari Liusvaara <ilari.liusvaara@elisanet.fi> Mon, 13 April 2015 19:17 UTC

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Date: Mon, 13 Apr 2015 22:17:33 +0300
From: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
To: Martin Thomson <martin.thomson@gmail.com>
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Subject: Re: [TLS] 0-RTT (Was: Re: 0-RTT and Anti-Replay)
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On Mon, Apr 13, 2015 at 11:24:13AM -0700, Martin Thomson wrote:
> On 13 April 2015 at 11:11, Ilari Liusvaara <ilari.liusvaara@elisanet.fi>; wrote:
> 
> > Also, there's the case 0-RTT is attempted without resumption. Or is
> > 0-RTT intended only for session resumption attempts (which would cut
> > quite a bit of complexity)?
> 
> I don't know how this is intended to work, but I always think of 0-RTT
> as resumption.  Nothing much else makes sense.
>
> >> That combination might not be valid.  If it is, I'm guessing that the
> >> first client flight is encrypted and authenticated as a "normal" 0-RTT
> >> handshake.
> >
> > One can't attempt resumption with 0-RTT data?
> 
> I don't actually know the answer to this.

There are three kinds of ClientHellos:
1) Those that attempt resumption (session-id or session-ticket)
2) Those that don't (no session-id, no session-ticket).
3) Some new type that doesn't currently exist (I presume TLS 1.3 won't
   add one).

Is attempt to send 0-RTT data allowed with 1)? With 2)?


-Ilari