The growth of wireless networks has been considerable over the last decades. Due to the broadcast nature of these networks, security issues have taken a critical role in today’s communications. A promising direction towards achieving secure communications is information theoretic secrecy, which an approach is exploiting the randomness of the channels to ensure secrecy. Based on this approach, there has been a recent surge of interest in a potential cooperation between users to enhance the secrecy of communications. In this thesis we investigate the interaction between cooperation and secrecy. In particular the contributions of the thesis can be divided into two parts. The problems of jamming beam-former design and power allocation are investigated jointly for two scenarios where the eavesdropper has either a single or multiple antennas, with the assumption that the global channel state information is available. Cooperative wireless networking improves the system operation efficiency and reliability by acquiring more and timely information. This project exploit physical layer security to provide secure cooperative communication for wireless ad hoc networks (WANETs). The transmission involves multiple source-destination pairs and malicious eavesdroppers. This system proposes the Smart jamming algorithm to interfere the eavesdropping channels. This project enhances the facility to increase the system secrecy capacity under various network settings. The main objective of this project is to exploit the secure issue with the presence of multiple eavesdroppers in WANETs. Increase the system secrecy capacity. To increase the primary channel capacity than the capacity of eavesdroppers channel.