From: cman@communities.com (Douglas Barnes)
Date: Sat, 30 Sep 95 10:43:08 PDT
To: Simon Spero <ses@tipper.oit.unc.edu>
Subject: Re: Crypto hardware (was: Using sound cards to accelerate RSA?)
Message-ID: <v02120d01ac933d63d4d3@[199.2.22.120]>
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Simon--

There is a lot more to cryptography hardware than just making
stuff go fast. Any kind of co-processor array could handle the
job -- doesn't have to be DSPs. For unsigned integer math, the
486 DX4/100 is a perfectly decent chip, and prices are plumetting.
If all you want is to make RSA go fast, you can rack up as
many of these as you want, and do your work at Ethernet speeds
(which should be more than fast enough for the forseeable future.)
Also, you get to use your old familiar (and inexpensive) programming
tools to write your code.

It also turns out that when you're actually using cryptography to do
valuable stuff, a lot of other concerns are just as
important as speed -- in particular, physical security over the
private keys. Most server-oriented cryptography add-ins are highly
tamper-resistant units that can only be re-keyed when some sort
of dongle is attached. Said dongle can be kept much more securely
than a whole computer. Although other threats still remain, this
substantially reduces the threat of key compromise. Incidentally,
good hardware of this sort uses ASICs that give substantially more
bang for the buck than the DSP solutions you're suggesting.

Certainly messing around with DSPs is fun -- I've done it and
enjoyed it -- but I don't think they will ever be significant as
cryptographic co-processors.

>That's another question. A DSP chip can also be used for crypto - yet
>sound cards and nexts aren't ITARed, and aren't really considered
>dual-use. A Modular exponentiator isn't a crypto device  (hey -
>it's a bignum accelerator for Mathematica). Now, if I had a pipelined
>WSI chip capable of delivering one result per cycle, I could think of
>some useful applications, but ...
>
>Simon