Wireless Channel-Based Physical Layer One-Time Pad Encryption Scheme for Modulated Signals

This paper proposes a novel physical layer one-time pad (OTP) encryption scheme for modulated signals based on the wireless channel. By imitating the OTP encryption for bit sequence, the sufficient conditions of perfect encryption for modulated signals are provided and proved. Then, we provide a detailed process of the scheme in the wireless system. Since the plaintext is the modulated signal rather than the bit sequence, we use high-level quantized channel estimation samples as secret keys and design encryption functions for QAM and PSK signals. The theoretical proof and Monte Carlo simulation results show that the proposed scheme can achieve perfect secrecy by designing the ciphertext signal independent of the plaintext signal. Furthermore, the simulation shows that the error probability of the proposed scheme is lower than that of the current mainstream physical layer encryption scheme because  the quantization level is optimized according to the signal-to noise ratio.