An approach for establishing secure multicast communication among multiple members that participate in a multicast group is disclosed. In one feature, multiple multicast proxy service nodes (MPSNs) are defined and control when members join or leave the multicast group. The MPSNs are logically represented by a first binary tree in which each node of the first binary tree is associated with a domain of a directory service and one or more of the MPSNs. A second binary tree is created that has leaf nodes representing each member. The second binary tree is stored in a domain of the directory service with a root node that represents one or more of the MPSNs. The members can each establish multicast communication and serve as a key distribution center. When a member joins the multicast group, a new group session key is determined by replicating a branch of the second binary tree.