FreAuth⁺: A Robust Frequency Feature-Based Device Authentication Mechanism for Magnetic Wireless Power Transfer System

Device authentication is critical for preventing unauthorized access and ensuring streamlined operation in magnetic wireless power transfer (WPT) systems. However, existing authentication techniques often suffer from security vulnerabilities and lack compatibility with low-cost receiver devices, limiting their practical applications. In this paper, we introduce FreAuth⁺ (FREquency feature-based AUTHentication), a novel authentication mechanism tailored specifically for magnetic-based WPT systems. Our approach involves acquiring impedance solely at the transmitter side without requiring active cooperation from the receiver. Using a dual-frequency interleaved subtraction technique, we eliminate ideal receiver impedance to reveal subtle frequency characteristics. These frequency features are then normalized to mitigate the effects of device positioning, and a temperature compensation method is applied to account for thermal variations. This process enables the generation of a robust hardware fingerprint based on frequency characteristics. For authentication, we employ a discrete Fréchet distance-based algorithm for effective fingerprint matching. We also develop a prototype of FreAuth⁺ and conduct extensive experiments. The results demonstrate its reliability, achieving 96.23% authentication performance across more than 60 devices with an average response time of 1.6 seconds. Furthermore, FreAuth⁺ exhibits excellent stability, effectively mitigating interference caused by device payload, device positioning, and temperature variations.

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