Prover anonymous and deniable distance-bounding authentication
Résumé
In distance-bounding authentication protocols, a verifier assesses that a prover is (1) legitimate and (2) in the verifier's proximity. Proximity checking is done by running time-critical exchanges between both parties. This enables the verifier to detect relay attacks (also called mafia fraud). While most distance-bounding protocols offer resistance to mafia, distance, and impersonation attacks, only few protect the privacy of the authenticating prover. One exception is the protocol due to Hermans, Peeters, and Onete, which offers prover untraceability with respect to a Man-in-the-Middle adversary. However in this protocol as well as in all other distance-bounding protocols, any legitimate verifier can identify, and thus track, the prover. In order to counter the threats of possible corruption or data leakage from verifiers, we propose a distance-bounding protocol providing strong prover privacy with respect to the verifier and deniability with respect to a centralized back-end server managing prover creation and revocation. In particular, we first formalize the notion of prover anonymity, which guarantees that even verifiers cannot trace provers, and deniability, which allows provers to deny that they were authenticated by a verifier. Finally, we prove that our protocol achieves these strong guarantees.