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

Martin Thomson <martin.thomson@gmail.com> Mon, 13 April 2015 19:57 UTC

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Date: Mon, 13 Apr 2015 12:57:51 -0700
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From: Martin Thomson <martin.thomson@gmail.com>
To: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
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Subject: Re: [TLS] 0-RTT (Was: Re: 0-RTT and Anti-Replay)
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On 13 April 2015 at 12:46, Ilari Liusvaara <ilari.liusvaara@elisanet.fi>; wrote:
> On Mon, Apr 13, 2015 at 12:30:04PM -0700, Martin Thomson wrote:
>> On 13 April 2015 at 12:17, Ilari Liusvaara <ilari.liusvaara@elisanet.fi>; wrote:
>> > 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)?
>>
>> You assume that 0-RTT doesn't fall into that third category.  I hadn't.
>
> Well, the only examples of 3) I can come up with would be
> - Resumption-only (fail enteriely if not resumable)
> - Something possibly triggering some new type (neither 1RTT, 2RTT
>   nor abbrevated) of handshake.
>
> Of course, I then have trouble even thinking what such new type
> of handshake could be.

Well, 0-RTT could be a third category.  As Hugo originally proposed
it, this would have the authentication of the connection be based on
successfully proving the ability to generate g^xy.  That's stronger
than resumption, but relies on the authentication of a previous
session in the same way that resumption does.  You might consider that
to be resumption, or not.