Dynamic balanced key tree management for secure multicast communications

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.