A scalable and distributed multicast security protocol using a subgroup-key hierarchy

Abstract

In the present paper, a scalable protocol for securing multicast communication is proposed. The proposed protocol is based on the idea of dividing the whole group into smaller subgroups as in the Iolus protocol. For a member join or leave, the decomposition of the group into smaller subgroups will reduce the computation complexity from O( M), where M is the number of the whole group members, to O( N), where N is the number of the subgroup members. Moreover, each subgroup is organized in a logical key hierarchy as in the LKH protocol. The use of logical key hierarchy will reduce the computation complexity cost from O( N) to O(log( N)) in case of member leave/join. Furthermore, the number of communicating messages containing the changed keys will be reduced. The proposed protocol is compared with the two well-known protocols: Iolus and LKH. The comparison is undertaken according to two criteria: the cost of encryption required for the re-key operation in case of member join or leave and the length of the re-key message. The results show that the proposed protocol outperforms both the Iolus and the LKH protocols. Therefore, the proposed protocol will enhance the group performance in terms of computation and communication.