Providing secure communications in mobile ad hoc networks (MANET) is an important and difficult problem, due to a lack of a key management infrastructure. The authentication is an important security service in (MANETs). To provide a node authentication service we use a fully distributed certificate authorities (FDCA) based on the threshold cryptography. In this paper we propose an efficient and verifiable multi secret sharing scheme in cluster-based MANET with a low computation system. Our scheme is based on the overdetermined linear system equation in Galois fields GF(2 r). We have analyzed our scheme based on security and performance criteria, and compared with existing approaches. The efficiency of our proposed schemes was verified and evaluated by simulation. Simulation results show that this approach is scalable.