Re: [TLS] TLS 1.3 - method to request uncached shared secrets

Eric Rescorla <ekr@rtfm.com> Sun, 19 July 2015 12:57 UTC

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References: <201507180037.56413.davemgarrett@gmail.com> <CAFewVt72efH+9qYzCSBh1heM7N9Ki-6VrVxbAc0=4UcSf5XbVg@mail.gmail.com> <201507181428.40766.davemgarrett@gmail.com> <20150719125016.GA17542@LK-Perkele-VII>
From: Eric Rescorla <ekr@rtfm.com>
Date: Sun, 19 Jul 2015 14:56:22 +0200
Message-ID: <CABcZeBMDujpLqQBtsWG+vutVM8V3g69Ys0_teZ4or=dU-uRwNQ@mail.gmail.com>
To: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
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Cc: "<tls@ietf.org>" <tls@ietf.org>
Subject: Re: [TLS] TLS 1.3 - method to request uncached shared secrets
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I'm not seeing a lot of value here. Remember that servers are not
required (and have never been required) to do session resumption, but
much of the overhead of doing it (having to have a database, session
ticket machinery) is associated with being willing to do session
resumption at all, so if a small fraction of clients would tell
you that they're not interested in resumption, it's not clear that
buys you much.

Are there any server operators who think this is a useful feature
and can explain why?

-Ekr


On Sun, Jul 19, 2015 at 2:50 PM, Ilari Liusvaara <
ilari.liusvaara@elisanet.fi> wrote:

> On Sat, Jul 18, 2015 at 02:28:40PM -0400, Dave Garrett wrote:
> > On Saturday, July 18, 2015 01:06:33 am Brian Smith wrote:
> > > This is not really what I was intending when I suggested the feature.
> I was
> > > intending for their to be an indication, in the ClientHello, that the
> > > server should not do any of the work that it would normally do to make
> the
> > > session resumable.
> >
> > Ok, I might as well write up the generic solution then:
> >
> >
> https://github.com/tlswg/tls13-spec/compare/master...davegarrett:sessionrequest
>
> Are the features besides "don't bother making resumable session, I won't
> resume." needed?
>
> E.g. For what would client hinting session lifetime be useful for?
>
>
> -Ilari
>
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