  This paper addresses an interesting security problem in wireless ad hoc
networks: the Dynamic Group Key Agreement key establishment. For secure group
communication in an Ad hoc network, a group key shared by all group members is
required. This group key should be updated when there are membership changes
(when the new member joins or current member leaves) in the group. In this
paper, We propose a novel, secure, scalable and efficient Region-Based Group
Key Agreement protocol (RBGKA) for ad-hoc networks. This is implemented by a
two-level structure and a new scheme of group key update. The idea is to divide
the group into subgroups, each maintaining its subgroup keys using Group
Diffie-Hellman (GDH) Protocol and links with other subgroups in a Tree
structure using Tree-based Group Diffie-Hellman (TGDH) protocol. By introducing
region-based approach, messages and key updates will be limited within subgroup
and outer group; hence computation load is distributed among many hosts. Both
theoretical analysis and experimental results show that this Region-based key
agreement protocol performs better for the key establishment problem in ad-hoc
network in terms of memory cost, computation cost and communication cost.
