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

Eric Rescorla <ekr@rtfm.com> Thu, 10 May 2018 11:49 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 10 May 2018 04:48:26 -0700
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To: Martin Thomson <martin.thomson@gmail.com>
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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 2:23 AM, Martin Thomson <martin.thomson@gmail.com>
wrote:

> 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.
>

Also, resumption of sessions created with PSKs

-Ekr


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