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.