Abstract-A secure multicast communication is important for applications such as pay-per-view and secure videoconferencing. A key tree approach has been proposed by other authors to distribute the multicast group key in such a way that the rekeying cost scales with the logarithm of the group size for a join or depart request. The efficiency of this key tree approach critically depends on whether the key tree remains balanced over time as members join or depart. In this paper, we present two Merging Algorithms suitable for batch join requests. To additionally handle batch depart requests, we extend these two algorithms to a Batch Balanced Algorithm. Simulation results show that our three algorithms not only maintain a balanced key tree, but their rekeying costs are lower compared with those of existing algorithms.

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Abstract-Secure multicast communication is important for applications such as pay-per-view distribution. LKH has been proposed to distribute a shared secret key in a way that scales efficiently for groups with many members. However, the efficiency of LKH depends critically on whether the key tree remains balanced. For applications such as video streaming or online teaching, several multicast sessions might be related in one way or another. In this paper, we consider the balance of the key tree and treat related multicast sessions as a whole. Our approach shows significant improvement over traditional method and trades off additional rekeying costs for similar computation power at members' side compared to existing related approach. Two optimisations are also proposed to further enhance the efficiency of our algorithm.

Secure multicast communication is important for both\ud wired and wireless applications. For groups with frequent join or depart requests, a distributed architecture that partitions the group members into several areas is preferred. Inside each area, scalable algorithms such as Logical Key Hierarchy (LKII) can be used to update the group key. However, these algorithms do not consider mobile members traveling in a Mobile Network as a whole. In this paper, we proposed two group key management schemes, which treat mobile members traveling in a Mobile Network as a whole. Both schemes try to reduce the communication costs when the Mobile Network moves in or out of the area. Simulation results show significant reduction in communications costs even for small number of mobile members\ud in the Mobile Network