Muon detection RNG ...

[bsr]

Looks pretty neat!  No extra radiation source needed, although the bit rate is a bit slow.

I found one a while ago that I thought was interesting.  Seems quite dated but still doable.  Doesn't look 100% open source but the main chip gets put on hold after initializing the LNB.

http://www.schlaupelz.de/TRNG/Highspeed_TRNG.html


Then there is always this:

http://phk.freebsd.dk/misc/DASK_rng.pdf