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Re: [TLS] TLS 1.3 multiple session tickets from the client?

Martin Thomson <martin.thomson@gmail.com> Thu, 10 May 2018 09:23 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Thu, 10 May 2018 09:23:14 +0000
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Subject: Re: [TLS] TLS 1.3 multiple session tickets from the client?
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On Thu, May 10, 2018 at 2:11 PM Viktor Dukhovni <ietf-dane@dukhovni.org>
wrote:
> TLS 1.3 allows clients to send multiple PSK identities, with the server
> choosing one.  When, if every, might it make sense for the client to
> send multiple session tickets to the server?  If this is not expected,
> is it sufficiently odd for a server to ignore any tickets after the
> first (if that one is not usable)?

NSS only looks at the first PSK offered by clients.  That is because we
primarily use PSK for session resumption.  I think that others do the
same.  I don't think that it makes a whole lot of sense to attempt to use
multiple PSKs in the context of resumption.

The option for multiple PSKs is something that is used in pure PSK modes,
but I confess to not fully understanding the reasons you might use multiple
PSKs.  I suspect that they are most useful during a key rollover.

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