Signcryption is an asymmetric cryptographic method that provides simultaneously both message confidentiality and unforgeability at a low computational and communication overhead. In this paper, we propose realistic security models for signcryption, which give the attacker power to choose both messages/signcryptexts as well as recipient/sender public keys when accessing the signcryption/unsigncryption oracles of attacked entities. We then show that Zheng's original signcryption scheme is secure in our confidentiality model relative to the Gap Diffie-Hellman problem and is secure in our unforgeability model relative to a Gap version of the discrete logarithm problem. All these results are shown in the random oracle model.
Signcryption proposed by Zheng REF at Crypto'97 is a public key or asymmetric cryptographic method that provides simultaneously both message confidentiality and unforgeability at a lower computational and communication overhead than doing signature and public key encryption separately.
Formal Proofs for the Security of Signcryption
Proceedings of Public Key Cryptography 2002 (PKC 2002), Vol. 2274 of LNCS, Springer-Verlag 2002
Computer Science