A mobile ad hoc network (MANET) is a network consisting of a collection of nodes capable of communicating with each other without the help from a network infrastructure. Although security issues in mobile ad hoc networks have been a major focus in the recent years, the development of fully secure schemes for these networks has not been entirely achieved till now. MANETs have a unique characteristics and constraints that make traditional approaches to security inadequate. The lack of an infrastructure exacerbates the situation of using shared secret keys or authentication among members. Therefore, the issues of authentication, key distribution and intrusion detection require different methods, which are discussed here. In this paper, we propose to combine efficient techniques from elliptic curve cryptography (ECC) and a distributed intrusion detection system (IDS) based on threshold cryptography. And also propose to use a distributed certifying authority (CA) along with per-packet per-hop authentication for addressing the issues mentioned above. The model assumes that no single node can be trusted and relies instead on a distributed trust model.