Wavelet-Based CSI Reconstruction for Improved Wireless Security Through Channel Reciprocity

Abstract: The reciprocity of channel state information (CSI) collected by two devices communicating over a wireless channel has been leveraged to provide security solutions to resource-limited IoT devices. Despite the extensive research that has been done on this topic, much of the focus has been on theoretical and simulation analysis. However, these security solutions face key implementation challenges, mostly pertaining to limitations of IoT hardware and variations of channel conditions, limiting their practical adoption. To address this research gap, we revisit the channel reciprocity assumption from an experimental standpoint using resource-constrained devices. Our experimental study reveals a significant degradation in channel reciprocity for low-cost devices due to the varying channel conditions. Through experimental investigations, we first identify key practical causes for the degraded channel reciprocity. We then propose a new wavelet-based CSI reconstruction technique using wavelet coherence and time-lagged cross-correlation to construct CSI data that are consistent between the two participating devices, resulting in significant improvement in channel reciprocity. Additionally, we propose a secret-key generation scheme that exploits the wavelet-based CSI reconstruction, yielding significant increase in the key generation rates. Finally, we propose a technique that exploits CSI temporal variations to enhance device authentication resiliency through effective detection of replay attacks.