On Wednesday 28 January 2009, Robert J. Hansen wrote: > Peter Thomas wrote: > > I've read about special hardware devices that (claim to) give true > > random numbers, some based on thermodynamics some even on quantum > > mechanics. > > True randomness exists in nature, but so far we're unable to detect > it. (Seriously.) > > Imagine you have a Geiger counter and a radioactive sample. Over > each time frame, the Geiger counter reports how many decays it > measures. That number becomes your random value. So far, so random, > right? > > But a Geiger counter has a reset time. Once it clicks, there's a > small time window in which it's unable to detect new decay events. > This has the effect of introducing a bias into your random number > generator: some decay events will be transformed into non-events. > > There are some tricks of physics and mathematics you can use to get > very high quality values out of this kind of radioisotope setup, but > the basic problem remains: even when measuring a totally > nondeterministic event, determinism in the detection mechanism will > undercut you. You can get really, really close to truly random > numbers, but you can't get there.
See http://www.fourmilab.ch/hotbits/ for a random number generator using radioactive decay. Under http://von-und-fuer-lau.de/ct-randcam.html you can download a (mostly) non-deterministic random number generator using a webcam. The page is in German. Regards, Ingo
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