[croikle]

This sort of thing is used, e.g. [0]. It collects entropy at a limited rate, though, so for demanding applications (SSL servers, say) you want dedicated hardware: [1], [2].

[0]: https://en.wikipedia.org/wiki/Hardware_random_number_generat...

[1]: https://en.wikipedia.org/wiki/RdRand

[2]: http://www.entropykey.co.uk/

[malandrew]

How do those Entropy Keys work? What sort of environmental random data does it rely on for creating random bits?

[wiml]

Thermal noise of various kinds, usually.

(Edit: that is, the noise introduced in a circuit by the fact that it's not at absolute zero, e.g. Johnson noise. Not just gathering entropy from a temperature sensor reading or something like that.)