Device-independent quantum key distribution based on Hardy's paradox

We present a secure device-independent quantum key distribution scheme based on Hardy's paradox. It has several novel, in comparison with protocols based on Bell inequalities, features: (a) The bits used for secret key do not come from the results of the measurements on an entangled state but from the choices of settings which are harder for an eavesdropper to influence; (b) Instead of a single security parameter (a violation of some Bell inequality) a set of them is used to estimate the level of trust in the secrecy of the key. This further restricts the eavesdropper's options. We prove the security of our protocol in both ideal and noisy case.