Re: [Cfrg] ed448goldilocks vs. numsp384t1 and numsp512t1

Michael Hamburg <mike@shiftleft.org> Tue, 21 October 2014 17:12 UTC

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From: Michael Hamburg <mike@shiftleft.org>
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To: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
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Subject: Re: [Cfrg] ed448goldilocks vs. numsp384t1 and numsp512t1
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> On Oct 21, 2014, at 4:09 AM, Ilari Liusvaara <ilari.liusvaara@elisanet.fi> wrote:
> 
> On Mon, Oct 20, 2014 at 03:48:48PM -0700, Michael Hamburg wrote:
>> 
>> On Oct 20, 2014, at 2:24 PM, Ilari Liusvaara <ilari.liusvaara@elisanet.fi> wrote:
>>> 
>>> On Sat, Oct 18, 2014 at 08:30:17PM -0000, D. J. Bernstein wrote:
>> 
>>>> Also signature verification:
>>>> 
>>>>   624000 cycles claimed: numsp384t1 (ed-384-mers),    ~2^192 security.
>>>>   729152 cycles measured on h6sandy: ed448goldilocks, ~2^224 security.
>>>>  1320000 cycles claimed: numsp512t1 (ed-512-mers),    ~2^256 security.
>>> 
>>> Here Ed448 seems to be slightly slow for some reason.
>>> 
>>> I would have estimated (on very dubious grounds) ~680k.
>> 
>> For verification, Goldilocks has to decompress and ECCLib doesn’t,
>> which costs almost 10%.
> 
> Signature verification uses double-sclar multiply, right?
> 
> Is your ds multiply constant-time? Because the one in ECClib
> apparently isn't (everything else should be).
> 
> 
> -Ilari

Yeah, it uses pretty much the same WNAF algorithm ECCLib uses, but it burns 60 or 70kcy first to decompress the public key.

— Mike