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Date: Wed, 30 Oct 2013 14:07:28 +0100
From: Katja Malvoni <kmalvoni@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: ZedBoard: bcrypt

On Wed, Oct 30, 2013 at 10:17 AM, Solar Designer <solar@...nwall.com> wrote:

> On Tue, Oct 29, 2013 at 07:48:35PM +0100, Katja Malvoni wrote:
> > At the moment performance is 602 c/s, maximum frequency is 100 MHz.
>
> What has contributed to doubling the performance (since your previous
> report)?  I guess it could be performing the 4 S-box lookups all at
> once, but then you're giving high numbers of cycles per round anyway:
>

That is correct, since most of the RAM is unused I'm storing each S-box
twice.

> I can't get one cycle delay block RAM to work. I also tried using RAM
> > module from http://openwall.info/wiki/crypt-dev/files but on Zynq it has
> > delay of 2 cycles. Same is with all the others variants I tried.
> > Currently one BF round takes 3 cycles - two for reading data from S-box
> > (I'm using two block RAMs so all 4 values are fetched in those 2 cycles)
> > and one to compute L and R when data is available.
>
> I'm not sure I understand how you're counting cycles here.  Let's look
> at one Blowfish round on its own.  Are you doing this? -
>
> Cycle 0: initiate 4 S-box lookups
> Cycle 1: wait
> Cycle 2: compute new R; swap L and R
>
> Cycle 3: ready to start next round (initiate 4 S-box lookups, etc.)
>

Yes, I am.


> If so, does anything prevent you from optimizing this to? -
>
> Cycle 0: compute new R; swap L and R; initiate 4 S-box lookups
> Cycle 1: wait
>
> ... except possibly for the special cases of the first and the last
> round?  In the first round, bypass some of the logic.  After the last
> round, invoke the same logic, but bypass the S-box lookups.
>

As far as I can tell nothing prevents me to do that, I'm on it now.

Katja

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