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Re: [TLS] Using Brainpool curves in TLS

Manuel Pégourié-Gonnard <mpg@elzevir.fr> Wed, 16 October 2013 14:25 UTC

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Date: Wed, 16 Oct 2013 16:25:10 +0200
From: Manuel Pégourié-Gonnard <mpg@elzevir.fr>
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To: Tom Ritter <tom@ritter.vg>, Johannes Merkle <johannes.merkle@secunet.com>
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Cc: Patrick Pelletier <code@funwithsoftware.org>, "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Using Brainpool curves in TLS
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On 16/10/2013 15:32, Tom Ritter wrote:
> I'm not sure I agree with them fully, but I also don't have very much
> context. (My thoughts when reading that is "Why sqrt(2) and sqrt(3)
> instead of pi and e - what makes those constants more trustworthy?")
> 
I think the point is not that sqrt(2) and sqrt(3) would be better constants that
pi, e, or any other constant. It's just that there are a few bits of freedom in
the choice of parameters, which makes the curve "not fully rigid".

This is obviously not a security concern unless you believe there is a class of
weak curves with quite high density, which would IMO be very bad news for ECC in
general, not only these particular curves.

Which is probably why the authors of the page chose a nice green color and check
symbol for both "fully rigid" and "somewhat rigid", as opposed to the
frightening red color of the other classe of curves.

Manuel.

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