Encryption-Aware PHY Security for Wiretap Channels with Multiple Independent Jammers

In conventional physical layer security schemes no leakage of private information to adversary nodes is tolerated, and no assumption on the encryption of information is considered. This is a limiting assumption in physical layer security, which compromises the efficiency of such schemes. This paper introduces an approach in which a prior knowledge of encryption can be used to improve the security performance of cooperative jamming in Gaussian wiretap channels as an example of physical layer security approached. The proposed approach, however, is not limited to the considered scenario of cooperative jamming and can be applied to other scenarios. We consider a system composed of a transmitter, a receiver, and eavesdropper and several jamming nodes that work independently, and formulate an optimization problem to maximize the secrecy rate with the knowledge of encryption and attempt to solve it by driving the rate-equivocation region to constrain and determine the feasibility of the solution. We then exploit a linear approximation to solve the resulted nonconvex optimization problem to maximize the secure transmission rate. Our numerical results show that prior knowledge of encryption can be exploited to allocate the available power to the jamming nodes to significantly increase the secure transmission rate.