On 4/15/15, The Doctor <drwho@virtadpt.net> wrote:
... I've gotten some success with a USB enabled Geiger counter (https://www.sparkfun.com/products/11345). A little Python was used to open the USB serial device and measure the amount of time that passed in between characters being emitted, hash them, and cat the hashes into /dev/random to give the kernel pool a little more to work with. The unit's pretty large (larger than the RasPi) and needs a housing of some kind to really protect it. I wouldn't use it for an HSM but for experimenting at home it works decently well.
the Pi has built-in camera capability; see the other threads about LEDs into a CCD for stochastic measurement at high rates. as amusing as ionizing radiation may be for entropy generation, there are much more practical routes :P
Now I just need to get around to learning SciPy to profile the output of /dev/urandom for biases...
DIHARDER over gigs will give you a great gist. is there a specific type of (transient) bias you're after?