Top-Level Secure Certificateless Signature Scheme in the Standard Model

In order to overcome the key escrow problem, Al-Riyami and Paterson introduced the concept of certificateless public key cryptography (CL-PKC) in 2003. CL-PKC requires neither public key certification nor the key escrow problem. After that, CL-PKC has been widely applied. In 1991, Girault defined three security levels of the key generation center (KGC), where the higher level of KGC means the stronger security of the system. Recently, lots of certificateless signature schemes and their security models have been presented. However, there is no certificateless signature scheme proposed in the literature that achieves the property of Girault's level-3 security without random oracles. In view of aforementioned issues, we propose a new construction of certificateless signature scheme. The proposed certificateless signature scheme is provably secure in the standard model and satisfies Girault's level-3 security. The security of the proposed scheme is based on the hardness of generalized computational Diffie-Hellman and many Diffie-Hellman problems.