An efficient and provably secure ID-based threshold signcryption scheme

Abstract

Abstract-Signcryption is a cryptographic primitive that performs digital signature and public key encryption simultaneously, at a lower computational costs and communication overheads than the signature-then-encryption approach. Recently, two identity-based threshold signcryption schemes [12], [26] have been proposed by combining the concepts of identitybased threshold signature and signcryption together. However, the formal models and security proofs for both schemes are not considered. In this paper, we formalize the concept of identitybased threshold signcryption and give a new scheme based on the bilinear pairings. We prove its confidentiality under the Decisional Bilinear Diffie-Hellman assumption and its unforgeability under the Computational Diffie-Hellman assumption in the random oracle model. Our scheme turns out to be more efficient than the two previously proposed schemes.