Alternative Entropy Sources

Question

Okay, I guess this is entirely subjective and whatnot, but I was thinking about entropy sources for random number generators. It goes that most generators are seeded with th

Answer 1

The Wikipedia article on Hardware random number generator's lists a couple of interesting sources for random numbers using physical properties.

My favorites:

• A nuclear decay radiation source detected by a Geiger counter attached to a PC.
• Photons travelling through a semi-transparent mirror. The mutually exclusive events (reflection — transmission) are detected and associated to "0" or "1" bit values respectively.
• Thermal noise from a resistor, amplified to provide a random voltage source.
• Avalanche noise generated from an avalanche diode. (How cool is that?)
• Atmospheric noise, detected by a radio receiver attached to a PC

The problems section of the Wikipedia article also describes the fragility of a lot of these sources/sensors. Sensors almost always produce decreasingly random numbers as they age/degrade. These physical sources should be constantly checked by statistical tests which can analyze the generated data, ensuring the instruments haven't broken silently.