Proficient Key Tree Structure for Dynamic Multicast Groups

Most of the group key management schemes focus on reducing the update messages. Majority of the groups are dynamic in nature and large. To assuage the scalability problem, various key structures have been proposed. In dynamic multicast groups, key updates are complicated since group members join and leave at any time. Hierarchical tree structure is suitable for maintaining multicast group members and keys. If the member wishes to join, it sends request to the Group Centre (GC) or Key Server. The Server authenticates the member and assigns an inimitable ID, which is later inserted into the tree. Similarly, the Server adjusts the tree when the member leaves from the group. Forward and backward secrecy are ensured by updating the keys whenever a join/leave request is handled called re-keying. Proficient Key Tree structure is proposed to reduce the number of re-keying operations during join/leave operations. This tree structure has two parts namely the upper part called quad tree at few levels which has at most four children and the lower part called a binary tree which has at most two children. With this structure, experimental results show that the costs are reduced compared to the full binary key tree approach.