phc-discussions - Re: [PHC] Updated tests document

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Date: Tue, 07 Apr 2015 08:02:36 +0200
From: Milan Broz <gmazyland@...il.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Updated tests document

On 04/06/2015 11:54 PM, Solar Designer wrote:
> Milan,
> 
> On Mon, Apr 06, 2015 at 11:10:27PM +0200, Milan Broz wrote:
>> I updated PHC candidates test output for the previously discussed tests
>>
>>   https://github.com/mbroz/PHCtest/blob/master/output/phc_round2.pdf
>>
>> - added "normalized" test from tables in http://article.gmane.org/gmane.comp.security.phc/2550
>> - fixed Lyra2 to us just one thread
>> - added memory/time combined chart
>> - added Argon2 git versions (just for comparison)
>> - added more functions to KDF example
>>
>> Otherwise it is kept in the same format.
> 
> This is good stuff.  Thank you!
> 
> When you provide speeds for "Reference" implementations, in yescrypt's
> case is this -ref or -opt?  I ask since yescrypt is unusual in providing
> 3 implementations currently: -ref (not for use at all, beyond testing),
> -opt (for non-SIMD builds), and -simd (for SIMD builds).

It is -ref (and the SSE is yescrypt-simd).

BTW simd version seems to not "easily" provide way how to decrease
PWXrounds (in other two it is just define, here is more complex macro IIRC).

> If -ref starts being benchmarked, this gets me thinking that maybe I
> should drop it in favor of -opt. ;-)  But that's counterproductive in
> terms of providing an implementation that is easier to read and is more
> self-contained (-ref does not use the yescrypt-platform.c functions,
> whereas -opt and -simd do).

Well, yes. Anyway, for x86 it is simd version what matters here.

I think that there are more important criteria than just speed,
readability is very important. (That said, I should probably run
test for all 3 implementations...)

Well, if algorithm is very slow (and it is clear that optimization cannot fix it)
then it is probably a problem but it is not the case for yescrypt.

I am a little bit scared of another things... like using reduced-round algorithms
elsewhere but that's just me. :)

> I think it makes more sense to list speeds for non-SIMD vs. SIMD builds,
> because non-SIMD builds may actually be in use (e.g., if someone builds
> a program that is meant to be portable to older CPUs).
> 
> yescrypt-ref.c even has:
> 
> $ fgrep warning yescrypt-ref.c
> #warning "This reference implementation is deliberately mostly not optimized. Use yescrypt-best.c instead unless you're testing (against) the reference implementation on purpose."

Yes, it is printed. I mention it in document that it is just reference.

> which gets printed during build.  I think it's not the same kind of
> thing as other candidates' non-SIMD implementations.  -opt is more
> similar to those.

If it makes sense, I'll just add the -opt variant there.
(The former intention was to compare it produces as the same output
as the optimized variant.)

Milan