DFT-based physical layer encryption for achieving perfect secrecy

We present a novel physical layer encryption (PLE) scheme that randomizes the radio signals using a discrete Fourier transform (DFT) based encryption algorithm. For any baseband signaling method, we show that perfect secrecy is asymptotically achievable with the proposed DFT-based encryption method when the signal block length (N) approaches infinity. For practical systems with finite N, we also show that the proposed encryption method can transmit at a secrecy rate close to the main channel's achievable data rate. In this sense, transmission privacy is achieved without compromising the capability of the communication channel. Besides, the proposed encryption method can hide the transmission data rate and is immune to all existing upper-layer attacks. The performance advantages of the proposed DFT-based encryption method is verified through comparisons against other existing PLE methods.