Secure group communication with multiplicative one-way functions

Secure group communication enables only the users in that group securely communicate with each other. Because the users can join or leave the group dynamically, scalability is a major concern. In this paper, we propose a communication-efficient model using multiplicative one-way functions. It also has well known tree-based structure but uses exclusive keys that are held by the users not in some subtree. When totally n users are in the group, proposed model reduces the size of multicast message required in join or leave operation from O(logn) to O(1) keeping other costs comparable. The security of proposed model is based on the difficulty of finding square root modulo composite number and it also satisfies both forward and backward secrecy. Therefore, proposed model is very applicable to a wide area network environment or a low-bandwidth channel such as ad hoc network.