Efficient lattice‐based authenticated key exchange based on key encapsulation mechanism and signature

Authenticated key exchange protocol is widely applied in the Internet services. Lattice‐based key exchange protocols turn out to be quantum‐resistant and hence have attracted tremendous attention. A lattice‐based explicit authenticated key exchange protocol is constructed by combining an IND‐CPA key encapsulation mechanism with a strong EUF‐CMA digital signature under the message‐recovery mode. Concrete parameter specifications are suggested under the 102 and 218 bits post‐quantum security, respectively. Compared with the implicit authenticated key exchange derived directly from the key encapsulation mechanism, our proposals reduce the communication costs by 21.7% and 25.7%, respectively, under the same post‐quantum security level. Rough analysis shows that the proposals also obtain some advantages over previous constructions in term of computational efficiency. Moreover, our scheme achieves perfect forward secrecy while the original scheme only satisfies weak forward secrecy.