At 12:32 PM 9/9/2013, Juan Garofalo wrote:

very naive question here :
Wouldn't it be possible to build a RNG using something like a zener diode and a $2 microcontroller?

Sure, and if you like playing with Arduinos and similar electronics, it'd be a good experiment.

The main issues you run into (besides getting a decent fast USB interface without having to use surface-mount electronics, which are annoying to solder),
are validating the quality of the randomness and getting enough speed to be useful (which depends not only on your noise quality but also on whether you're using a USB-enabled chip or just bit-banging.

DieHard http://en.wikipedia.org/wiki/Diehard_tests is probably still the standard quality test - your noise is almost certain to be biased, rather than purely uniform, so you'll need to whiten the data and adjust your entropy estimates appropriately.