Physical Layer Secret Key Exchange Using Phase Randomization in MIMO-OFDM

In wireless communication systems, secret key is used to protect confidential transmission. The process of securely exchanging these key bits is critical. Most existing methods require cumbersome calculations which may not be appropriate for limited power devices. In this paper, we propose a physical layer key exchange method which transmits the key bits by encoding them within some phase randomization sequences that are selected according to a certain channel criterion. The phase randomization sequences only randomize the data phases and thus no efficiency reduction will be incurred. The proposed is demonstrated within the context of multiple-input multiple-output orthogonal frequency division multiplexing (MIMO- OFDM) system. The results reveal that, relative to existing techniques, this method offers superior performance and lower computational complexity.