COOPERATIVE relaying is gaining a significant attention in that multiple intermediate relay nodes can collaborate with each other to enhance the overall network efficiency. It exploits the physical-layer broadcast property offered by the wireless Tradeoff Between Reliability and Security in Multiple Access Relay Networks Under Falsified Data Injection Attack medium that transmitted signals can be received and processed by any node in the neighborhood of a transmitter. The cooperative relaying approach has a great potential to provide substantial benefits in terms of reliability (diversity gain) and rate (bandwidth or spectral efficiency). These benefits can extend the coverage, reduce network energy consumption, and promote uniform energy drainage by exploiting neighbors’ resources. They can be of great value in many applications, including ad-hoc networks, mesh networks, and next generation wireless local area networks and cellular networks. In multiple access relay networks, relay nodes may combine Tradeoff Between Reliability and Security in Multiple Access Relay Networks Under Falsified Data Injection Attack the symbols received from different sources to generate parity symbols (packets) and send them to the destination. Then, the destination may use the network generated parity symbols (packets) to enhance the reliability of decoding. While this technology is promising in improving communication quality, it also presents a new challenge at the physical layer due to the dependency of the cooperation. Tradeoff Between Reliability and Security in Multiple Access Relay Networks Under Falsified Data Injection Attack That is, reliance on implicit trust relationship among participating nodes makes it more vulnerable to falsified data injection. Although this might also occur in a traditional system without cooperative communication, its effect is far more serious with cooperative communication. If a false packet is injected into the buffer of a node, the output of the node will become polluted, and this may soon propagate to the entire network. The problem of detecting malicious relay nodes in singlesource, Tradeoff Between Reliability and Security in Multiple Access Relay Networks Under Falsified Data Injection Attack multi-relay networks has been studied in the literature for different relaying strategies . Relay nodes in apply network coding while those in follow the decode-and-forward protocol. In , the authors consider a peer-to-peer (P2P) network in which peers receive and forward a linear combination of the exogenous data packets. To check the integrity of the received packets, a signature vector is generated at the source node and broadcasted Tradeoff Between Reliability and Security in Multiple Access Relay Networks Under Falsified Data Injection Attack to all nodes where it is used to check the integrity of the received packets. In , several information theoretic algorithms for mitigating falsified data injection effects are proposed. The network model used in these works is composed of a single source, multiple intermediate nodes which apply network coding.