Summary: A mobile ad hoc network (MANET) is a collection of mobile nodes that forms a provisional network dynamically without the aid of any predetermined infrastructure. The salient nature of ad hoc networks renders them vulnerable to numerous types of security attacks. The dynamic feature of ad hoc networks makes enforcement of security become an extremely challenging issue. The main problem of many proposed routing protocols for ad hoc networks is that these protocols have critical susceptibilities to security attacks. Effective operation of ad hoc networks depends on the maintenance of correct routing information of the network. Nevertheless, securing routing protocols without securing network transmissions is not enough. As a result, our major focuses are to secure the routing protocol and likewise to protect data transmission. In this paper, we present the secure routing protocol (SEROP), which achieves data confidentiality and secures the routing protocol for mobile ad hoc networks without demanding any unrealistic assumptions.