This study addressed security requirements for ad-hoc network environments, which lies at the hour of the ubiquitous computing revolution and proposed a partially-distributed certificate management system that can ensure security in mobile ad-hoc networks. The proposed model is characterized by ie ability to handle dynamic mobility of nodes, minimize routing load and enhance expandability of network by allowing participating nodes to authenticate each other without being interrupted by joining the cluster. The security, efficiency and robustness of the proposed model were evaluated through simulation.