Summary: Efficient access control with scalable rekeying is one of the most important requirements for secure group communications, especially in a dynamic and large group. In a many-to-many group communication environment, sender authentication is also another important security requirement as each participant can potentially be both a sender and a receiver. In this study, we propose an authenticated group communication scheme which is secure against an adaptive chosen ciphertext attack using identity-based signcryption. The proposed scheme allows multiple senders to dynamically multicast messages into an arbitrary group of receivers determined by the senders. In the proposed scheme, the group member can be a stateless receiver. Data confidentiality of the group communication is guaranteed as well as the sender authentication.