Scalable secure one-to-many group communication using dual encryption

Multicasting is a scalable solution for group communication. Whereas secure unicast is a well-understood problem, scalable secure multicast poses several unique security problems, namely group membership control, scalable key distribution to a dynamic group. We address scalability in the proposed protocol by using hierarchical subgrouping. Third party hosts or members of the multicast group, designated as subgroup members, are responsible for secret key distribution and group membership management at the subgroup level. Unlike existing secure multicast protocols, our protocol, through dual encryption, can use `untrusted' subgroup managers (SGMs) to distribute data encryption keys securely. We analytically prove the correctness of the protocol in ensuring secure communication, describe possible collusion scenarios and our protocol's ability to overcome them. We compare our protocol with existing scalable key distribution schemes through simulation using real-life multicast traces and show that our protocol alleviates the encryption overhead at the sender by distributing some of the work among the SGMs. The proposed protocol performs better than the existing scalable protocols as the number of active members in a multicast group increases.