Mobile ad hoc network (MANET) is a collection of mobile hosts without any existing infrastructure or centralized access point such as a base station. MANET is an emerging research area because of their self configuration and self maintenance capabilities. However the wireless ad-hoc network is more vulnerable to security than conventional wired and wireless networks due to its characteristics like open medium, lack of centralized monitoring, wireless and dynamic nature. Routing security is an important issue in MANET. The primary function of a routing protocol is to establish a secure and efficient route between communicating nodes so that data may be delivered correctly. Existing routing protocols need security mechanism to guard against external and internal attacks but it is very difficult to find a general idea that can prevent efficiently all types of attacks, as each attack has its own distinct characteristics. In this paper, we proposed a method that is based on ad hoc on-demand routing (AODV) protocol and can efficiently prevent the attacks from member of the network including black hole, modifying routing information and impersonation attacks. The proposed method uses only hash function and thus provides fast message verification and sender as well as intermediate nodes authentication. Simulation result shows that in the presence of malicious node, the proposed method performs better than the original AODV protocol.