[4582] in cryptography@c2.net mail archive
Re: forwarded message from Steven M. Bellovin
daemon@ATHENA.MIT.EDU (Brad Martin)
Sat May 1 12:50:20 1999
Date: Fri, 30 Apr 1999 16:49:34 -0500
From: Brad Martin <brad@nshore.com>
To: "Steven M. Bellovin" <smb@research.att.com>
Cc: Jim Thompson <jim@wayport.net>, mctylr@privacy.nb.ca, Rob_Lemos@zd.com,
cryptography@c2.net, linux-ipsec@clinet.fi
This is a multi-part message in MIME format.
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Hi,
I'm Brad. We did the "Atom-Age RNG" box. Jim
Thompson forwarded your mail regarding his
comment about us:
>>Here in my hands, I have an "Atom-Age" HW RNG device.
> Sounds interesting -- do you have a URL or other contact info?
Regarding self-test, no, it's really a simple
box. I just wanted to get the numbers right.
No whitening, just straight bits. I'm a big
fan of raw numbers. I'm completely wigged-out
about the concept of performing whitening
before a user sees numbers.
I understand the desire for self-validation in
the box, I just wasn't headed there myself.
I've always believed that this sort of thing
is best done explicitly by the user.
Doing the tests one's self - Doctor's advice
even with a "fancy" RNG - this is NOT MEANT as
a catty remark, but I REALLY THINK this is
important. (you didn't trust us, did you? :-)
Rhetorically, what's the point of testing your
RNG at power-up? Either the circuit is good or
it's bad. Who's to say that a circuit that can't
be trusted to start-up and spit-out good random
numbers won't start spitting-out bad numbers
during normal operation?
I'd much prefer to have the host checking the
numbers as a matter of normal operation. I'm
not too thrilled about expecting the RNG to
check itself, in any situation.
About the only thing that hoses up the numbers
in my box is low batteries. For that reason, I
put hardware in the box to constantly monitor
the three separate & isolated power supplies.
The uP shuts things down if any of the power
supplies go too low.
Personally, I've gotten so used to the way it
works (I've been using it for more than three
years) that I just don't worry about the
numbers on my own box much any more. I've run
this thing through muck and mire, finding that
if the micro hasn't shut things down because of
a power supply problem, the numbers are going
to be good.
If someone can put together a streaming test
for up on the host computer (*nix and/or 9X/NT)
and would be kind enough to provide source code,
I'd be highly gratified, and thankful. I would
of course gladly send it along with the boxes
as a way of helping out those who don't want to
worry about or think too much about this issue.
All our uP does is collect the bits and run an
RS-232 port. Plus a little bit of housekeeping.
You get the uP source code & it's documented
(imagine that). Worried? Careful? Buy the $99.00
microprocessor development kit from Motorola,
scan in the text, audit it, reassemble it & burn
a new uP. We chose the uP and even socketed the
uP for that exact reason (the kit includes an
assembler, a programmer and a blank uP!).
The board comes with schematics. There's even
a breadboarding area for experimentation. Want
to play with high-dollar noise diodes? Change
the amplifiers? It couldn't be easier, get out
a soldering iron.
A few other nice features. Big steel box. Thick
steel. Dangerous in flight.
This is a labor of love and you're welcomed
to join in. I do keep a few dozen or so in
stock and they're easy to build: custom steel
CNC box fabrication, volume manufacturing on
line, etc. If I needed to, I could and gladly
would make them in the thousands.
Thank goodness, though, it's been fun to do.
Especially since the odds of making back even
the development costs are 10e6-to-1.
Essentially, I wanted to answer the question:
"If it's so easy to do this with just a diode,
why doesn't anybody make a cheap box that does
that?"
Unfortunately, it took me about two solid months
of engineering work to provide the answer, being
that it takes a lot of focused effort to get
a reproduceable circuit with numbers that are
really good and to get that circuit into a form
ready for volume production. Add to that the
distinct possibility that I'll only sell a few!
What the heck, it's only a $200 box. Big deal.
But, I've found that it's really a fine little
box for what it is.
I do sincerely appreciate your interest.
Best regards,
Brad Martin
NSCD LLP
P.S. Atom-Age is a small company we run on the
side. You can get more information on who we are
by going to our REAL company's web site, at:
www.nshore.com.
P.S.S. Of course, I'm sure that a lot of the
people using the Intel stuff will check their
numbers, too - no matter how good they say they
are - but that's the kind of guys we are :-).
If they're good numbers, I think that (in
general term) the work by Intel is a very good
thing to have happened. - b.
P.S.S.S. I hope the Intel RNG isn't a pseudo
RNG hash of the PID ;-) - b.
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