[Cryptography] Fun with hardware RNGS: the Infinite Noise Multiplier

[Bill Cox]

Someone asked for some more detail about the design.  I've created a simple
web page describing the Infinite Noise Multiplier here:

http://dev.vinux-project.org/RNG/

Surely someone else has already invented this.  Anyone know where I could
find
such a circuit described on the Internet?

Bill


On Thu, Dec 5, 2013 at 9:24 PM, Bill Cox <waywardgeek at gmail.com> wrote:

> I'm naming this circuit after my daughter.  We're a whole family of
> severely ADHD people!
>
> I've been trying to crack a simple problem for a few years, thinking about
> it now and then: how do you generate "true" random numbers on an analog
> CMOS process designed to be "quiet"?  In 1998, I built a 4-megabit/second
> hardware RNG that destroyed the DieHard tests back then (I found bugs in
> the prof's code, rather than his code finding bugs in my hardware).  It
> relied on zener noise from a breakdown of a Vbe on a N2222 transistor.
>  Every process is different, so I had potentiometers for tweaking gains and
> such.  It was a sweet little board, but not mass-production ready.
>
> So, here's my dumb infinite noise multipier.  It's a switched cap circuit
> doing the following steps:
>
> - Start with a voltage V > 0, but < Vref.
> - Multiply V by 2X.
> - If V > Vref, subtract Vref
> - Repeat forever
>
> The RNG output is 1 whenever we have to subtract Vref, and 0 otherwise.
>  If there is a tiny bit of noise way down in say the 35th bit position of
> resolution, then about 35 cycles later, that noise will impact the output
> signal.  It really doesn't matter how quite the circuit is.  Enough cycles
> later, you're output will be banging around quite randomly, kind of like
> some people I know.
>
> Just some fun for the day... true RNGs in ANY process is now very simple...
>
> Bill
>
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