the first device-independent protocol proposed was device-independent quantum key distribution (qkd). in this primitive, two distant parties, alice and bob, are distributed an entangled quantum state, that they probe, thus obtaining the statistics formula_44. based on how non-local the box formula_44 happens to be, alice and bob estimate how much knowledge an external quantum adversary eve (the eavesdropper) could possess on the value of alice and bob’s outputs. this estimation allows them to devise a reconciliation protocol at the end of which alice and bob share a perfectly correlated one-time pad of which eve has no information whatsoever. the one-time pad can then be used to transmit a secret message through a public channel. although the first security analyses on device-independent qkd relied on eve carrying out a specific family of attacks, all such protocols have been recently proven unconditionally secure.