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Re: [TLS] Singular or multiple NamedGroup(s) in the "HelloRetryRequest"

Eric Rescorla <ekr@rtfm.com> Fri, 16 January 2015 18:19 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Fri, 16 Jan 2015 10:18:49 -0800
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To: "Dang, Quynh" <quynh.dang@nist.gov>
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Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Singular or multiple NamedGroup(s) in the "HelloRetryRequest"
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On Fri, Jan 16, 2015 at 9:59 AM, Dang, Quynh <quynh.dang@nist.gov> wrote:

> Hi Eric and Henrik,
>
> That would be fine. I just read the description of the "Client Key Share
> Message" again, It does not reflect the intent (to me); I found the
> description confusing, not clear.
>

That's too bad. If you have some editorial improvements, a pull request
would
be appreciated.

Best,
-Ekr

Quynh.
>
>
>
> ________________________________________
> From: Henrik Grubbström <grubba@gmail.com>
> Sent: Friday, January 16, 2015 11:44 AM
> To: Dang, Quynh
> Cc: Eric Rescorla; tls@ietf.org
> Subject: Re: [TLS] Singular or multiple NamedGroup(s) in the
> "HelloRetryRequest"
>
> On Fri, Jan 16, 2015 at 4:51 PM, Dang, Quynh <quynh.dang@nist.gov> wrote:
> > If a client offers all of the options it supports and a server sends back
> > one group out of these options, it would guarantee a failure.
>
> It seems you've misunderstood; the client announces all named groups
> that it supports in the named_group extension, but usually only
> provides a subset of these in its ClientKeyShare message. Thus the
> server can ask for a named group that the client supports but hasn't
> provided a key share for in its HelloRetry.
>
> /grubba
>
> --
> Henrik Grubbström                                       grubba@grubba.org
> Roxen Internet Software AB                              grubba@roxen.com
>

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