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Re: [TLS] Remove EncryptedExtensions from 0-RTT

Ilari Liusvaara <ilariliusvaara@welho.com> Thu, 23 June 2016 10:35 UTC

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Date: Thu, 23 Jun 2016 13:35:46 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Martin Thomson <martin.thomson@gmail.com>
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Subject: Re: [TLS] Remove EncryptedExtensions from 0-RTT
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On Thu, Jun 23, 2016 at 01:37:14PM +1000, Martin Thomson wrote:
> When implementing 0-RTT, an in particular the ticket_age extension, we
> discovered that this greatly increases the complexity of the server
> state machine. 
> 
> David Benjamin rather flippantly described a solution to this problem:
> XOR the ticket age value with something that is either derived from
> the old session keys or was included in the NewSessionTicket message.
> 
> I propose we take David's solution.  After all, simple is better:
> 
>   https://github.com/tlswg/tls13-spec/pull/503

I don't see a warning that reusing a ticket with that scheme causes
the "masking" to break (the classic "multiple time pad" broken scheme).


-Ilari

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