Re: [Cfrg] A2 versus A^2 and BB verus AA

Samuel Neves <sneves@dei.uc.pt> Sat, 10 January 2015 21:31 UTC

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Date: Sat, 10 Jan 2015 21:31:13 +0000
From: Samuel Neves <sneves@dei.uc.pt>
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Subject: Re: [Cfrg] A2 versus A^2 and BB verus AA
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On 01/10/2015 08:42 PM, Tanja Lange wrote:
>> Whether it works out or not, it's good to match EFD. I've updated the
>> draft in GitHub to match, thanks!
>>
> This is not a typo, it is using a different (better) definition
> of the curve constant which is what the implementations use.

Not trying to turn this into another pointless discussion, but the choice of a24 seems 50/50 in actual implementations.
From the current SUPERCOP version:

 - amd64-51: 121666
 - amd64-64: 121666
 - athlon: 121665
 - costigan-schwabe: 121666
 - donna: 121665
 - donna_c64: 121665
 - neon2: 121666
 - ref: 121665
 - ref10: 121666

All of these were written by experts. What makes 121665 better?

Best regards,
Samuel Neves