BatchAuth: A Physical Layer Batch Authentication Scheme for Multiple Backscatter Devices

Backscatter communication (BC) offers a promising power-efficient communication paradigm for wireless devices with constrained energy resources. However, the innate openness and broadcast characteristics of BC raise considerable security concerns. To address this, physical layer authentication has emerged as a primary solution to enable secure BC. To facilitate efficient authentication on multiple backscatter devices (BDs), batch authentication becomes essential. Nevertheless, existing schemes have not yet bridged the research gap regarding effective batch authentication on mobile BDs with high scalability support. This paper proposes BatchAuth, a physical layer batch authentication scheme designed to authenticate multiple BDs simultaneously by leveraging orthogonal frequency-division multiple access (OFDMA) technology. BatchAuth utilizes two factors, received signal strength (RSS) and multiple channel impulse responses (CIRs), to authenticate a group of BDs and leverages a channel correlation coefficient to offset performance loss and support BD dynamicity. What's more, a backscatter waveform design facilitates an access point (AP) in estimating the CIRs from backscattered signals. Additionally, BatchAuth possesses the capability to detect and trace potential attackers by analyzing the specific characteristics of orthogonal subcarriers to facilitate countermeasure. In particular, BatchAuth demonstrates significant potential on scalability in large-scale BC systems and multiple-input multiple-output (MIMO) systems. Theoretical analysis on BatchAuth security and extensive simulations under various settings by comparing with cutting-edge schemes further validate its commendable performance with regard to accuracy, robustness, efficiency, and scalability.