🚀 go-pugleaf

On a visit to the Exploratorium in San Francisco last week (the
occasion was an excellent Interop hospitality "suite" sponsored by
TGV, by the way) I got an inspiration for yet another hardware random
number generator.

One of the exhibits was a "chaotic pendulum" consisting of several
interconnected pendulums. (penduli?) Spin it and the whole ensemble
twists and contorts in all sorts of bizarre ways. Although a simple
pendulum is highly predictable, a coupled set of pendulums is very
different.  It's a good demonstration of chaos theory, in that very
small variations in initial starting conditions yield very different
outcomes over time. Just the ticket for a good hardware random number
generator.

Just attach an optical shaft encoder (the more bits the better) to the
main pivot. Spin it and sample the encoder after several seconds.
Repeat several times, concatenate the encoder values, and hash with
MD-5. The result should be a pretty good random number, suitable for
use as a crypto key. Of course, you'll want to keep the blinds drawn
so the FBI can't videotape your key generator in action...

Phil