For simple electronics circuits, reverse-biasing a transistor past its breakdown voltage will give you "noise" — an ADC will give you random values.
I don't know how statistically random it is — suspect it is quantum in nature though since we're dealing with transistors.
(EDIT: checked with ChatGPT, has a sense of humor: "Be careful not to exceed the maximum reverse voltage ratings, or you’ll get more “magic smoke” than white noise.")
Most any sensor attached to a realworld physical system can produce sufficient randomness. Put a vibration sensor on my clothes dryer, plug the output into an md5 hash, and voila. Or setup a webcam aimed at a tree blowing in a breeze. Or pour out some m&ms onto a table and photograph that. We dont need to go quantum when sufficiently random systems like turbulance exist in the macro world.
Thanks, I always associated it with GitHub (as having "done it first" but didn't really think to push further). I appreciate the correction, I like knowing the correct information.
i used software defined radios to make a few sets of one time pads with entropy. The randomness of proper SDR or even a webcam in a lightproof coffee can or something is demonstrable with any of the tools for "testing randomness"; sibling is correct, MEMS are notorious for "noise" and that noise is "random", one can use a GM tube to trigger interrupts and use the timing to get entropy.
I don't know how you'd prove something is truly random, though, just that it looks and acts "random" enough; fitness for use.
I don't know how statistically random it is — suspect it is quantum in nature though since we're dealing with transistors.
(EDIT: checked with ChatGPT, has a sense of humor: "Be careful not to exceed the maximum reverse voltage ratings, or you’ll get more “magic smoke” than white noise.")