Re: [TLS] sect571r1

mrex@sap.com (Martin Rex) Thu, 16 July 2015 00:21 UTC

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To: Tony Arcieri <bascule@gmail.com>
Date: Thu, 16 Jul 2015 02:20:56 +0200 (CEST)
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From: mrex@sap.com (Martin Rex)
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Subject: Re: [TLS] sect571r1
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Tony Arcieri wrote:
[ Charset UTF-8 unsupported, converting... ]
> Dave Garrett <davemgarrett@gmail.com> wrote:
>> 
>> It's the most used of the rarely used curves.
> 
> 
> I think all "rarely used curves" should be removed from TLS. Specifically,
> I think it would make sense for TLS to adopt a curve portfolio like this:
> 
> - CFRG curves (RECOMMENDED): Curve25519, Ed448-Goldilocks
> - NIST curves (SUPPORTED): P-256, P-384, P-521

P-256 and P-384 seem to be pretty important to some folks
(those with a NIST/NSA Suite B checklist).  I'm OK with P-521,
but I would prefer to get rid of pretty much all _other_
NIST curves with unexplained parameters, including 571

Either the NIST curves with unexplained constants _are_ backdoored,
then you get screwed no matter which one of them you use.
Or the NIST curves are OK, then P-521 will be good enough.  IMO.

-Martin


Microsoft SChannel seems to implent the 3 NIST curves (P-256, P-384, P-521),
and MSIE 10 exhibits a curious behaviour on my Win7 machine:
when only TLSv1.0 is enabled, then MSIE 10 sends a ClientHello
with P-521 as the first curve in the named_curve extension.
when TLSv1.2 is also enabled, then MSIE 10 sends a ClientHello
with P-256 as the first curve in the named_curve extension.