We propose and analyze a scalable and efficient cluster-based group key management protocol for secure group communications in mobile ad hoc networks. For scalability and dynamic reconfigurability; we take a cluster-based approach by which group members are broken in to cluster-based subgroups and leaders in subgroups securely communicate with each other to agree on a group key in response to membership change and member mobility events. We show that secrecy requirement for group communication is satisfied. Further, there exists an optimal cluster size that minimizes the total network communication cost as a result of efficiently trading inter-regional vs. intra-regional group key management overheads. We give an analytical expression of the cost involved which allows the optimal cluster size to be identified, when given a set of parameter values characterizing a group communicating system in mobile ad hoc networks.

Many mobile wireless applications nowadays are based on secure group communication by which data is encrypted using an encryption key (called a group key). When a member joins a group, the group key is re keyed so that the new member cannot decrypt the previous messages. This is meant by Backward Secrecy. When a member leaves a group, the group key is re keyed so that the leaving member could not decrypt the messages in future. This is meant by Forward Secrecy.In this paper we propose a reliable and secure cluster-based group key management protocol for secure group communication in mobile ad “hoc networks (MANET). We also propose a Contributory Key Agreement protocol (CKA) for key generation instead of a centralized key server. We break a group in to cluster-based subgroups with a leader in each group. Any changes in these groups will be recorded as a membership change event and other event changes. Each group has a group key and each leader in a group has a leader key, there is also cluster key to identify the clusters. Each of these keys contains information about Id™s of a cluster, group or member.

Conceivably, as the number of group members becomes large, group key management can incur significant overheads and cause a potential system performance bottleneck. For scalability and dynamic management, we propose a two level hierarchical key management architecture adopted from the IETF Group Key Management Architecture to efficiently and securely distribute keys. In our protocol, a leader communicates with the members in the same region using a cluster key. All leaders in the group use a leader key, KLR, for communications among leaders. A group key, KG, is derived from the leader key KG =MAC (KLR, c), where KLR is a leader key and c is a counter to be incremented whenever a group membership change event occurs. The group key (KG) is used for Secure data communications among group members. These three keys are re keyed for secure group communications depending on events that occur in the system.