AKE Protocol Combining PQC and QKD

With the advent of quantum computing, which threatens the very foundations of classical cryptography, several authenticated key exchange (AKE) protocols have been proposed, combining classical and post-quan­tum cryptographic algorithms, and a quantum key distribution (QKD) sub-protocol. The goal being to associate the claimed information theoretic security of QKD, and the security based upon computational assumptions of classical and post-quantum cryptography. To our knowledge, in existing security proofs of such hybrid AKE protocols, the QKD phase is treated as a black box and the impact of establishing the output quantum key appears similar as setting a symmetric key beforehand at the two communicating parties. In this paper, we describe an hybrid AKE protocol and a security model that captures multiple security properties. Our security analysis integrates the security loss induced by the QKD phase as well as that of implied by the classical and post-quantum cryptographic algorithms involved in the protocol.