Privacy-preserving WiFi sensing in WSNs via CSI obfuscation

Abstract

WiFi’s inherent openness introduces significant privacy risks from unauthorized sensing, driving considerable research efforts to mitigate these threats. However, the latest spatial obfuscation schemes like repeater-based signal forwarding and beamforming control ones have limitations in recovering legitimate sensing and maintaining communication performance respectively. To address these challenges, this paper presents a privacy-preserving WiFi sensing framework, which supports shielding unauthorized sensing while allowing normal communication and legitimate sensing. It uses a dynamic channel obfuscation technique at the transmitter side, which filters the whole frame including the Long Training Sequence (LTS) to perturb Channel State Information (CSI) while ensuring receiver equalization decoding for communication performance. Moreover, a deep network-based de-obfuscation approach is employed to support legitimate sensing. This approach models the nonlinear relationship between obfuscation response and tap coefficients to accurately predict the original CSI, addressing issues like deviations due to hardware defects and phase unavailability due to transceiver separation. The proposed framework has been rigorously tested in real-world scenarios, whose effectiveness is evaluated through indoor localization experiments conducted on the Software Defined Radio (SDR) platform. The results indicate that the framework can diminish eavesdroppers’ sensing performance to below 50%, while maintaining legitimate sensing performance above 90%. This work advances dual-functional WiFi systems by establishing the hardware-compatible architecture that fundamentally resolves the privacy-utility conflict through three key innovations: (1) formalized CSI obfuscation with provable communication preservation, (2) physics-informed nonlinear deobfuscation network architecture, and (3) comprehensive validation from PHY-layer security to application-layer functionality based on hardware implementation.