This chapter covers issues related to security in mobile ad hoc networks. It acts as a comprehensive survey material covering the cryptographic schemes and trust modeling techniques traditionally found in mobile ad hoc network (MANET) survey articles. The need for hybrid security techniques, involving both cryptographic approach and trust based model, in a resource constrained ad hoc network, is also emphasized in this work. Additionally, the lack of realism in the research works related to ad hoc network security is also pointed out. The state of the art in ad hoc security should employ hybrid techniques that can be easily implemented in an ad hoc network. This will lead to the large scale deployment of mobile ad hoc networks in various context-aware applications. © 2012, IGI Global.