Security in Low-Altitude ISAC with Coupled Communication and Sensing Information Leakage

Secure information transmission in integrated sensing and communication (ISAC) systems deployed in low-altitude wireless networks (LAWN) is particularly challenging due to the open airspace and the broadcast nature of wireless signals reused for both communication and sensing, which give rise to more severe and complex security threats. This paper investigates the joint communication and sensing security of low-altitude ISAC systems where a communication eavesdropper (CEve) cooperates with and assists a sensing eavesdropper (SEve), leading to coupled communication and sensing information leakage. We define a recoverable signal power ratio (RSR) that quantifies the degree of coupling between communication eavesdropping and sensing information leakage. Based on this coupling, we formulate a joint eavesdropping mutual information (MI) that facilitates unified analysis and optimization for the overall security. Subsequently, we design the transmit beamformer that maximizes the weighted sum of legitimate communication and sensing MI under the joint information-leakage constraint. Simulations show that the proposed scheme converges rapidly and effectively exploits the coupling between communication eavesdropping capability and sensing information leakage.