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

Martin Thomson <martin.thomson@gmail.com> Wed, 22 June 2016 00:44 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Wed, 22 Jun 2016 10:44:00 +1000
Message-ID: <CABkgnnXdFJHEA60x-KObf_dT1aS5ys49mO4Uffmmw4sKwNX8Yg@mail.gmail.com>
To: Watson Ladd <watsonbladd@gmail.com>
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Subject: Re: [TLS] Simpler backward compatibility rules for 0-RTT
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On 22 June 2016 at 10:27, Watson Ladd <watsonbladd@gmail.com> wrote:
> Isn't 0-RTT refusable? Why not treat 1.2 negotiation as a refusal?

The problem isn't that you get a 1.2 ServerHello, it's what happens
after that.  The server is going to choke on your 0-RTT data when it
receives that instead of the client's second flight.  If it doesn't,
it's probably passing your 0-RTT ciphertext to the application as
plaintext and that's even worse.

I don't expect people to update their 1.2 implementations to be able
to ignore 0-RTT data.

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