Re: [Cfrg] Chopping out curves

Michael Hamburg <mike@shiftleft.org> Thu, 16 January 2014 21:54 UTC

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From: Michael Hamburg <mike@shiftleft.org>
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Date: Thu, 16 Jan 2014 13:53:51 -0800
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To: Trevor Perrin <trevp@trevp.net>
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Subject: Re: [Cfrg] Chopping out curves
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On Jan 16, 2014, at 1:50 PM, Trevor Perrin <trevp@trevp.net> wrote:

> On Thu, Jan 16, 2014 at 1:40 PM, Watson Ladd <watsonbladd@gmail.com> wrote:
>> Dear all,
>> Trevor Perrin suggests that we only put in Curve25519/T25519 and
>> E383/M382 so implementors can focus on 4 curves ala Suite B. Are there
>> any protocols in which larger curves would be useful? Anything we
>> might be missing with this decision?
> 
> I didn't quite suggest that.
> 
> I do feel there should be fewer curves.  Perhaps only curve25519 and
> (either Curve3617 or Ed448-Goldilocks).
> 
> It takes a great deal of effort to do high-speed, const-time
> implementations of a different curve, so we should not diffuse that
> effort across too many choices.
> 
> Note that Suite B only has 2 curves (P-256 and P-384).

Yeah, I was going to protest: instead of using one stronger Montgomery curve and one Edwards, maybe we should use a Montgomery curve and a birationally equivalent (or at least isogenous) Edwards curve, or vice-versa.

— Mike