An Enhanced Certificateless Signcryption in the Standard Model

Signcryption is a cryptography prototype which performs message encryption and signature in a logical step. Certificateless public key cryptography successfully resolves the problem of certificate management in traditional public key cryptography and key escrow problem in identity-based public key cryptography. There are lots of efficient certificateless signcryption schemes that have been proposed, most of which are proved secure under the random oracle model. But when applied in practical situations, the random oracle model will cause many security problems due to its own defects. Nowadays, more and more people pay attention to the standard model which provides a stronger security. In this paper, we present an efficient certificateless signcryption scheme that is provably secure in the standard model. Under the Decisional Bilinear Diffie-Hellman and Computational Diffie-Hellman hard problems, our scheme satisfies the ability of indistinguishability against adaptive chosen ciphertext attack and existential unforgeability against adaptive chosen message attack. Moreover, our scheme satisfies known session-specific temporary information security that most of signcryption schemes in the standard model cannot achieve this security attribute. Compared with other signcryption schemes, our scheme achieves shorter ciphertext length, better performance efficiency and stronger security.