Secret key generation based on wireless channel reciprocity is a promising area of research towards ensuring secure wireless communication. In this paper, we propose a method of generating secret keys using channel diversity obtained via millimeter wave (mmWave) beamforming at 60 GHz. The proposed method is simulated using the QuaDRiGa channel model considering an industrial non-line of sight (NLOS) environment. We verify the method by conducting experiments using a 60 GHz software-defined-radio (SDR) communication system with a linear phased-array-antenna of 16 dual patch elements. Further, we present a composite key generation method in which both the real and imaginary parts of the channel state information (CSI) are utilised, and several sub-keys obtained from individual beam directions are appended. As a result, we can generate long composite keys with high entropy and secrecy. The keys randomness are assessed employing the National Institute of Standards and Technology (NIST) statistical test suite, showing the generated keys are highly random.

mmWave Beamforming, Beam steering, Physical Layer Security (PLS), key generation, 60 GHz mmWave communication system.