Mobile ad hoc networks have unique features, such as variable topology and lack of centralized management, therefore key management faces additional difficulty for deployed in this environment. In this paper, a (n, t, n) secret sharing method is applied towards a group-based mobile ad hoc networks architecture to provide authentication and key management services. All nodes participate in key pair generation as shareholders using a threshold secret sharing scheme. This group-based network consists of multi-level participants. The nodes in different levels have different identities. The node identity in a higher-level subset is different from the larger common group. In the subset, shared information is broadcast efficiently and securely without risk of eavesdropping from larger group.