Efficient and Robust Physical Layer Key Generation

Physical layer key generation is a promising privacy protection technique suitable for devices with limited computational ability. In this work, we design a key generation algorithm based on orthogonal frequency-division multiplexing (OFDM) waveforms and implement the algorithm on a testbed. By exploiting the holistic channel state information (CSI), we improve the key generation rate (KGR) significantly. The performance of the algorithm and the secrecy of generated keys are evaluated by experimentation. Then, we design a cross-layer encryption protocol based on our key generation algorithm and the Advanced Encryption Standard (AES). We provide a mathematical framework to show that the secrecy of the encryption is enhanced compared to traditional encryption schemes with one pre-shared key (e.g., WPA2-PSK), even when some generated keys are leaked to the eavesdropper. The results lead to practical and robust applications of physical layer key generation.