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Date: Wed, 30 Oct 2013 19:28:52 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: bcrypt-parallella on 64-core (was: Katja's weekly report #13)

On Wed, Oct 30, 2013 at 01:55:51PM +0100, Katja Malvoni wrote:
> Another idea I have is to use local memory instead of external - with this
> approach I would avoid external loads completely.

Right, that's what you need to do in order to use all cores despite of
external loads to some cores being broken.

> But this approach failed
> with E16 because stack would overwrite part of S-box in some cases. But
> format would usually pass self test. I have that code somewhere so I'll
> modify optimized code accordingly and try this approach, it might work (at
> least for self test so that we can see performance).

I think it should be fairly easy to avoid the stack overwrite issue.
I think we didn't approach the full 32 KB usage closely enough for this
to be a difficult problem.  We're using 8 KB for the S-boxes, some
kilobytes more for code, and perhaps under 1 KB for other misc. data and
under 1 KB for stack (unless you inadvertently(?) place something large
on the stack).

Alexander

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