IDENTITY-BASED SIGNCRYPTION WITHOUT RANDOM ORACLES

The use of signcryption for secure and authenticated data communication was realized in 1997, following which numerous signcryptions have been presented which are provably secure in the random oracle proof methodology. In this paper, we present an identity-based signcryption provably secure in the standard model. Our scheme relies on the intractability of two well studied problems, the decisional bilinear Diffie-Hellman and the computational Diffie-Hellman. We achieve the security reduction of our scheme for the properties message confidentiality and unforgeability without relying on random oracles.