Certificateless signcryption scheme in the standard model

Certificateless public key signcryption scheme is an important cryptographic primitive in cryptography. Barbosa and Farshim proposed a certificateless signcryption scheme. However, their construction is proven to be secure in the random oracle model but not the standard model, and the scheme is also vunlerable to the malicious-but-passive key generation center (KGC) attacks. To overcome these disadvantages, we introduce a formal security model for certificateless signcryption schemes secure against the malicious-but-passive KGC attacks and propose a novel certificateless signcryption scheme. The proposed certificateless signcryption scheme is proven to be IND-CCA2 secure under the decisional Bilinear Diffie–Hellman intractability assumption without using the random oracles. The proposed scheme is also proven to be existentially unforgeable under the computational Diffie–Hellman intractability assumptions. Furthermore, performance analysis shows that the proposed scheme is efficient and practical.