Efficient and Secure Multi-Receiver Signcryption Scheme

In this paper, we propose an efficient multi-receiver signcryption scheme which can provide confidentiality and authenticity simultaneously. Compared with the trivial multi-receiver signcryption scheme, our scheme achieves much better efficiency. To address the security issue, we formulate the first security model for multi-receiver signcryption and define strong security notions. Then we prove that our scheme satisfies these security notions in the random oracle model. More specifically, in the sense of indistinguishability against chosen ciphertext attacks, our scheme is secure under the q-Diffie-Hellman inversion assumption. And in the sense of unforgeability against chosen message attacks, our scheme is secure under the q-Strong Diffie- Hellman assumption.