Encryption-Aware PHY Security: Optimal Cooperative Jamming and Achievable Rates

Conventional physical layer (PHY) security assumes unencrypted transmissions, requiring zero information leakage to adversaries. By incorporating encryption, this constraint can be relaxed, enabling higher secure transmission rates while tolerating limited leakage. This paper investigates an encryption-aware power allocation strategy and achievable transmission rate of a Gaussian wiretap channel in the presence of multiple cooperative jammers. By analyzing the rate-equivocation region and the corresponding rate maximization problem, optimal cooperative jamming strategy that maximizes the encryption-aware secrecy capacity is first addressed. The encryption-aware rate maximization problem is then shown to be equivalent to a non-convex beamforming vector optimization under a non-linear constraint, which is explicitly solved. Our numerical results illustrate that by utilizing the prior knowledge of encryption, optimizing the power allocation among jamming nodes significantly enhances the achievable secrecy rates.