In this paper, we present a secure group key management scheme for hierarchical mobile ad-hoc networks. Our approach aims to improve both scalability and survivability of group key management for large-scale wireless ad-hoc networks. To achieve our goal, we propose the following approaches: (1) a multi-level security model, which follows a modified Bell-La Padula security model that is suitable in a hierarchical mobile ad-hoc networking environment, and (2) a decentralized group key management infrastructure to achieve such a multi-level security model. Our approaches reduce the key management overhead and improve resilience to any single point failure problem. In addition, we have developed a roaming protocol that is able to provide secure group communication involving group members from different groups without requiring new keys; an advantage of this protocol is that it is able to provide continuous group communication even when the group manager fails. Key words: Security, Group k...