Security enhancement of a W-band millimeter-wave signal based on 3D Hilbert scrambling and diffusion

A physical layer enhancement scheme of the W-band millimeter-wave signal based on chaotic grouping and segmentation encryption, 3D Hilbert scrambling, and diffusion is proposed in this paper. Chaotic grouping and segmentation bit-level encryption can enhance the randomness of data and enlarge the key space. 3D Hilbert scrambling and chaotic diffusion are performed in symbol and subcarrier domains. The correlation of data can be effectively reduced after encryption. The analyses show that the key space of the proposed scheme can reach ∼10¹⁵². The encrypted W-band millimeter-wave signal can be successfully transmitted in the orthogonal frequency division multiplexing (OFDM) radio-over-fiber (RoF) system of 50-km standard single-mode fiber (SSMF) and 3-m wireless channel, and the experimental results demonstrate that the proposed scheme can enhance the security of the system without negatively affecting transmission performance.