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Re: [TLS] Security review of TLS1.3 0-RTT

Nico Williams <nico@cryptonector.com> Tue, 02 May 2017 18:20 UTC

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Date: Tue, 02 May 2017 13:16:53 -0500
From: Nico Williams <nico@cryptonector.com>
To: TLS WG <tls@ietf.org>
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Subject: Re: [TLS] Security review of TLS1.3 0-RTT
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On Tue, May 02, 2017 at 02:08:03PM -0400, Viktor Dukhovni wrote:
> > On May 2, 2017, at 1:52 PM, Colm MacCárthaigh <colm@allcosts.net> wrote:
> > it is not quite about the general use of tickets - only as they
> > pertain to 0-RTT data.  My understanding is that 0-RTT is not
> > particularly interesting for SMTP, so would that be ok?
> 
> Yes, if the change is narrowly tailored to 0-RTT, *and* if server TLS stacks
> don't stop supporting ticket reuse for "normal" (not 0-RTT) sessions, then
> I have no direct concerns with changes that affect 0-RTT alone.

In many environments (e.g., intra-corporate) the connection correlation
issue might not be a concern at all.  Though, of course, the default
should be (MUST) to assume that connection correlation is a concern.

So I would insist on the change being no stronger than "MUST NOT reuse
tickets with 0-rtt unless connection correlation is not an issue for the
application/user".

Nico
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