Re: [TLS] Simpler backward compatibility rules for 0-RTT

Martin Thomson <> Thu, 23 June 2016 21:03 UTC

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From: Martin Thomson <>
Date: Fri, 24 Jun 2016 07:03:38 +1000
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To: Watson Ladd <>
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Subject: Re: [TLS] Simpler backward compatibility rules for 0-RTT
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On 24 June 2016 at 00:26, Watson Ladd <> wrote:
> If we're
> willing to change the interaction pattern to support that, we can
> accommodate using 0RTT as an extension by gathering it all and sending
> when the handshake happens.

That's a very different constraint on the usage.  In one, you have to
identify data as being "for 0-RTT" very explicitly.  In the other, you
have to have all the data available when you send a ClientHello.  The
latter is rarely the case.

> But it sounds like you are discussing a
> design where the handshake fakes completion if 0-RTT is on, and at
> some point later "well, i didn't actually send the data you wanted
> to". Or am I missing something about the API design that is motivating
> this streaming approach?

I don't think that's what I'm suggesting.  I don't intend to change
the signals in the current draft, namely that the handshake indicates
the presence (ClientHello) and acceptance (ServerHello) of 0-RTT.