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Re: [TLS] draft-ietf-tls-tls13-21 posted

Matt Caswell <frodo@baggins.org> Tue, 04 July 2017 10:25 UTC

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From: Matt Caswell <frodo@baggins.org>
Date: Tue, 04 Jul 2017 11:25:35 +0100
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Subject: Re: [TLS] draft-ietf-tls-tls13-21 posted
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On 4 July 2017 at 01:01, Eric Rescorla <ekr@rtfm.com> wrote:
> - Modifying the key derivation for PSKs so that each session ticket
>   is associated with a distinct PSK.

Draft-21 says this about the ticket nonce:

          opaque ticket_nonce<1..255>;
...
   ticket_nonce  A unique per-ticket value.


Within what context is "uniqueness" required? I am assuming that
uniqueness within the context of a single TLS connection is all that
is needed?

The nonce can be anything between 1 and 255 bytes long. There is no
guidance on a suitable length, so I am assuming I can choose anything
I like as long as the uniqueness constraint is met. OpenSSL
(currently) only ever issues a single ticket per TLS connection so is
a single 0 byte sufficient?

Thanks

Matt

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