EntropyKey - miniature Windows driver...?

[Rob Kendrick]

On Mon, 12 Jul 2010 14:38:33 +0100
Nick Pelling <nickpelling at nanodome.com> wrote:

> >As I say, it's on the list of things we'd like to do, but haven't had
> >time to do yet.  The job is complicated somewhat because the Entropy
> >Key itself is complicated.  Other TRNG products are basically dumb
> >devices: they feed you random data over a serial port or similar.
> >The Entropy Key has a protocol with encryption and commands, and
> >requires a tool to configure them, monitor them, etc.  So just
> >writing a library that opens a serial port, reads some bytes, and
> >returns them, won't work here.
> 
> I'm a little surprised by this, because I've found that Cortex-M3 
> microcontrollers are surprisingly capable little beasts. If you
> reduced the effective maximum throughput you were hoping for, do you
> think the ARM (or rather, Thumb2) could do basically everything
> itself, or was that a design decision you consciously avoided?

I'm not sure I understand you.  We selected a Cortex-M3 microcontroller
(an STM32 in the Entropy Key's case) for several reasons:
	1) We already stock them, as we use them in other products,
	2) We are very familiar with ARM in general, having been
           producing ARM-based hardware for nearly 20 years,
	3) We have our own tool chain and development environment for
	   them,
	4) ST provide off-the-shelf code for emulating serial devices,
	5) It has plenty of number crunching power for the cryptography
	   that occurs inside the device itself.

Point 5 is why the Entropy Key is somewhat less trivial to drive than
most other similar products.  (Many of which have no CPU at all, and
just attach a noisy circuit directly to a serial port, and have the
UART do the analogue-to-digital conversion.)

-- 
Rob Kendrick, Support Team Lead                      Simtec Electronics
Telephone: +44 (0)1772 978013                  Avondale Drive, Tarleton
Fax: +44 (0)1772 816426                     Preston, Lancs, PR4 6AX, UK
http://www.simtec.co.uk/                       mailto:rjek at simtec.co.uk