[2207] in cryptography@c2.net mail archive
Re: DES, MMX, and FPGAs
daemon@ATHENA.MIT.EDU (Daniel R. Oelke)
Fri Feb 27 11:36:24 1998
Date: Fri, 27 Feb 1998 08:06:36 -0600
From: Dan.Oelke@aud.alcatel.com (Daniel R. Oelke)
To: ptrei@securitydynamics.com, cryptography@c2.net
>
> Some highly uninformed blather about FPGAs follows:
>
> Wiener's paper uses custom VLSI chips, and claims a need for
> 26k "gates" or 78257 "sites". I'm not sure how this translates to
> silicon requirements in FPGAs - it seems that "gate" and "site" are
> nominal terms which are not directly equivalent to actual, physical
> gates. I've found one reference to a general DES FPGA implementation
> which requires 25k gates, though it's not clear if this reuses the
> round circuitry, or 'unrolls' it (I suspect the latter, which would
> be good).
>
> I'm also not certain if a FPGA running at, for example, 50 MHz, can
> actually run logic operations at that speed. Some things I've read
> suggest that FPGAs run ops at several clocks per operation - which
> is still a lot better than a general purpose microprocessor.
Going from what I brother had run into trying to get a single DES
engine (doing 1 check / clock) into an FPGA he found that the
problem was not the number of gates. In fact, most of the gates
in his FPGA's were unused. The major problem was the routing.
He was (I *think*) using Altera FPGA's.... or maybe Xlinx....
(Damn I need to find that paper.)
This makes sense when you think about the DES algorithm. There
are lots of permutations. This means basically that there are
wires that need to cross one another. Not something that
FPGAs are particullarly efficient at.
> I'd really like to see the next DES challenge taken on by some
> organization with a few hundred under utilized FPGA boards.
Does anyone know of a commercially available FPGA board
that can be plugged into your PC? Some of the FPGA companies
have a few demos that they loan to schools, etc. but it seems
hard to find them on the general market.
Dan
--------------------------------------------------------------------------
Dan Oelke - droelke@aud.alcatel.com Alcatel Telecom, Richardson, TX
"... you'll love it ... it's a way of life ..."
- Joe's Garage, Act I Scene 1
