A New Multi-Receiver ID-Based Signcryption Scheme for Group Communications

Multi-receiver signcryption is very useful to secure group communications. In 2007, Yu et al. proposed an efficient multi-receiver identity-based signcryption scheme. However, Selvi et al. showed that Yu et al.'s scheme does not satisfy the unforgeability, and presented an improved scheme. In this paper, we show that both Yu et al.'s scheme and Selvi et al.'s scheme do not satisfy the confidentiality. Then we propose a new multi-receiver identity-based signcryption scheme. We prove its semantical security under the q-Bilinear Diffie-Hellman Inversion problem assumption and its unforgeability under the q-Strong Diffie-Hellman problem assumption in the random oracle model. This new scheme turns out to be more efficient than all other schemes proposed to date.