Perry writes, regarding alpha decay counts for random numbers:
And, as I noted, there are RS232 interfaceable radiation detectors you can buy off the shelf -- no hardware hacking needed.
As far as a radiation source goes, the Americium 241 source from a cheap smoke detector is just dandy. A while ago, I took one into the lab and put it on a scintillating counter and got alpha hits at roughly half-microsecond intervals. It was a while ago, so I forget how this compared to the rating in Curies on the package. But that would be fine for a low-to-moderate bandwidth RNG.
I was thinking about this the other day and wondered if it wouldn't be cheap and relatively easy to build a board that samples and sums several randomly selected signals on various frequencies on the AM broadcast spectrum. This should catch stations in nearly all metropolitan (and most rural areas as well) and would require that someone be able to broadcast at multiple frequencies to "cheat" it. Perhaps this would be affected by RF interference from the motherboard itself. If so, could the RF radiation from the motherboard itself be used to generate random numbers? -- Dave Dittrich Client Services, Computing & Communications dittrich@cac.washington.edu University of Washington <a href="http://www.washington.edu/People/dad/"> Dave Dittrich / dittrich@cac.washington.edu</a>