Provably Secure Certificateless Two-Party Authenticated Key Agreement Protocol without Pairing

Key agreement is one of the fundamental cryptographic primitives in public key cryptography. So far several certificateless two-party authenticated key agreement (CL-T-AKA) protocols have been proposed. However, all these protocols are based on bilinear map and most of them are without formal security proof. In this paper, we present a new formal security model of CL-T-AKA protocols and bring forward the first two-party key agreement protocol without the computation of expensive bilinear map. Our protocol is secure under the security model assuming the Gap-DH problem is intractable. With respect to efficiency, our protocol requires a single round of communication in which each party sends only one group element, and needs only five modular exponentiation computations. In addition, we point out that an existing certificateless two-party key agreement protocol cannot resist man-in-the-middle attack.