Improvement of the Naive Group Key Distribution Approach for Mobile Ad Hoc Networks

Most of mobile ad hoc network (MANET) applications are based on the group communication and, because of the insecure characteristic of the wireless channel, multicast security is especially needed in MANET. Secure delivery of multicast data can be achieved with the use of a group key for data encryption. However, for the support of dynamic group membership, the group key has to be updated for each member join/leave and, consequently, a mechanism distributing an updated group key to members is required. The two major categories of the group key distribution mechanisms proposed for wired networks are the naive and the tree-based approaches. The naive approach is based on unicast, so it is not appropriate for large group communication environment. On the other hand, the tree-based approach is scalable in terms of the group size, but requires the reliable multicast mechanism for the group key distribution. In the sense that the reliable multicast mechanism requires a large amount of computing resources from mobile nodes, the tree-based approach is not that desirable for the small-sized MANET environment. However, recent studies on the secure multicast mechanism for MANET focus on the tree-based approach. Therefore, in this paper, we propose a new key distribution protocol, called the proxy-based key management protocol (PROMPT), which is based on the naive approach and reduces the message overhead of the naive by introducing the concept of the proxy node.