Efficient Certificateless Signcryption from Bilinear Pairings

Certificateless public key cryptography is an attractive paradigm which combines advantages of both traditional certificate-based and ID-based public key cryptosystems. In this paper, the author formalizes the definition and the security model for certificateless signcryption (CLSC), and proposes a CLSC scheme that is proved to be secure in the random oracle model. The CLSC scheme satisfies such desirable properties as message confidentiality, signature unforgability, public verifiability and forward secrecy. Moreover, the scheme achieves significant efficiency in that it requires general cryptographic hash functions instead of the MapToPoint function which is inefficient and probabilistic, and the public/private key of a user in the scheme is a single group element, and it is unnecessary to check the validity of the public key, and signcryption algorithm needs no pairing operation while the reverse operation only requires two pairing computations.