It is of great importance to address the multi hop routing protocols in mobile ad hoc networks (MANET). Assuming secure wireless channel and trustable cooperative nodes in executing the protocol, helps to find the best path with minimum hop between source and destination, and utilize the network resources efficiently in order to improve the performance. Routing in MANETs faces a number of security attacks due to dynamic topology, lack of any infrastructure, wireless channels, anticipated cooperative nodes, and distributed environment in this kind of networks. Therefore, providing a tight security for these networks is an important issue. Throughout the last decade, a lot of works deal with solving the security problems of routing protocols in MANET. These works include proposing secure protocols, key management, trust management and intrusion detection systems. Utilizing different cryptography mechanisms such as Symmectric-key encryption, digital signatures, and hash functions in proposing secure protocols, and using intrusion detection systems are popular approaches for securing MANETs in the literature. However, in this work, by choosing one of the most common routing protocols, AODV, we evaluate the performance of the two security mechanisms, cryptography and intrusion detection, and we show how much using each of these approaches can be effective against various attacks. Considering these two approaches against threats, we propose two schemes in order to improve the performance. First, we present a mechanism for generating route-reply packets in SAODV, the secure version of AODV protocol. Second, we define and suggest an optimized feature set in order to improve the anomaly detection in the network. Finally, by addressing the advantages and disadvantages of these approaches in AODV and aiming an acceptable level of security, we propose a novel scheme which utilizes both cryptography mechanism and intrusion detection simultaneously. Keywords: Mobile Ad hoc Network (MANET), Security, AODV, SAODV, Intrusion Detection System
