Re: [Cfrg] Curve manipulation, revisited

Adam Langley <agl@imperialviolet.org> Sat, 27 December 2014 09:38 UTC

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Date: Sat, 27 Dec 2014 01:38:08 -0800
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From: Adam Langley <agl@imperialviolet.org>
To: David Gil <dgil@yahoo-inc.com>
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Subject: Re: [Cfrg] Curve manipulation, revisited
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On Fri, Dec 26, 2014 at 1:50 PM, David Gil <dgil@yahoo-inc.com>; wrote:
> I assume that you mean finite fields, not curves?
>
> (This would seem to be just as good of an argument for generating
> Edwards curves over the Salinas primes, which are rather widely
> implemented...)

Sharing the underlying field certainly helps reduce implementation
effort, but there's still lots more work than that, including all of
the duplication of test cases that inherently comes from each
additional curve.

(Not to mention that I consider the Salinas primes to be a bug-magnet
to such an extent that replacing the field in that case would probably
still be a net-positive for correctness.)

> Alas, no, I don't have that advantage: WebCrypto [has more-or-less
> decided][w3c_curves] that they will only implement CFRG-recommended
> curves. I need WebCrypto support -- for non-extractable keys.
> But I also need to have something that is relatively clean to
> implement in JS, for support of legacy-ish browsers.

I would currently expect Chrome to be in the "legacy" set if you want
WebCrypto support for a larger CFRG curve.


Cheers

AGL