Mobile ad hoc networks (MANETs) are finding growing applications in time-critical and mission-critical scenarios such as disaster rescue?C public safety and military operations. The purpose of this project is to investigate two very important but mostly untouched MANET security issues: user unlocatability and communication anonymity. Without solving them, mobile users can be easily tracked or their communication patterns can be easily gathered for user profiling, which would jeopardize the user privacy and make them vulnerable to pinpoint attacks. In this project, a novel overlay-based approach OverUCA, an anonymous network overlay composed of nodes that anonymously communicate with one another atop the underlying MANET substrate, will be investigated to achieve user unlocatability, source anonymity, destination anonymity, source-destination unlinkability, and full compatibility with existing routing and MAC protocols. The success of this research will have a tremendous impact on advancing the deployments of MANETs in security-critical commercial, civilian, and military applications. This research will provide a viable way to fight against pinpoint attacks, advance the state-of-the-art in the wireless security research, and spark new research activities in securing MANETs. Moreover, the results from this research will be disseminated widely through high-quality conference and journal publications and public talks. Furthermore, the research outcome will be integrated into the educational curricula across two institutions. Finally, a couple of minority (female) students will work for their Ph.D. degrees, and hence this project will train the minority professionals for the national work force.