Abstract: Signcryption is a cryptographic primitive which provides authentication and confidentiality simultaneously with a computational cost lower than signing and encryption respectively. The ring signcryption has anonymity in addilion to authentication and confidentiality, which allows any user to choose any set of users that includes himself and signcrypt messages without revealing who in the set has actually produced it. This paper presented an efficient identity-based ring signcryption scheme in the standard model, which proves its indistinguishability against adaptive chosen ciphertext attacks and existential unforgeability against adaptive chosen message and identity attacks in terms of the hardness of CDH problem and DBDH problem.

Key words: Ring signcryption, Standard model, Computational Diffie-Hellman problem, Bilinear pairing