Re: [TLS] Curve25519 in TLS

Rob Stradling <rob.stradling@comodo.com> Fri, 13 September 2013 09:27 UTC

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Date: Fri, 13 Sep 2013 10:27:37 +0100
From: Rob Stradling <rob.stradling@comodo.com>
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To: Nico Williams <nico@cryptonector.com>
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Cc: Simon Josefsson <simon@josefsson.org>, Patrick Pelletier <code@funwithsoftware.org>, "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Curve25519 in TLS
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On 12/09/13 22:12, Nico Williams wrote:
<snip>
> Of course, in practice it's much easier to deploy new ECDH curves for
> key agreement than new signature algorithms because the former are
> easily negotiated in actual protocols, while the latter are less so.

Disagree, I think.  Doesn't the "Supported Elliptic Curves Extension" 
make it easy enough for TLS?

RFC4492 (Section 5.3) says:
   "If the client has used a
    Supported Elliptic Curves Extension, the public key in the server's
    certificate MUST respect the client's choice of elliptic curves;"

So if a TLS Client advertises support for Simon's proposed Curve25519 
NamedCurve, then surely that Client is implying that it supports both 
Curve25519 for key exchange _and_ Curve25519 keys in certs?

> But, yes.
>
> Nico
> --

-- 
Rob Stradling
Senior Research & Development Scientist
COMODO - Creating Trust Online