 Bell’s theorem has played a direct role in the development of device independent quantum cryptography. One can exploit quantum correlations to devise a quantum key distribution protocol that is provably secure on the assumption that, whatever the underlying physics is, it does not permit superluminal signalling. The basic idea is that, if one has Bell inequality-violating correlations at spacelike separation, any predictability of the results beyond that afforded by the quantum probabilities could be exploited for superluminal signalling; the contrapositive of this is that impossibility of signalling entails “absolute randomness” — absolute in the sense of being independent of the details of the underlying physics beyond the prohibition on superluminal  signalling.[9] 