Seven‐Dimensional Hyperchaotic Physical‐Layer Encryption for Secure Hybrid Fiber–THz–Fiber Communications

ABSTRACT With the evolution of 6G communications toward ultrahigh speed, ultralow latency, and wide‐area coverage, information security faces increasing challenges from emerging attacks. To address these issues, this paper proposes a physical‐layer encryption scheme based on a seven‐dimensional (7‐D) hyperchaotic system for 6G full‐link fusion transmission architectures, including Fiber–THz Wireless, THz–Fiber Wireless, and Free‐Space Optical (FSO) links. The dynamical properties of the proposed system are analyzed through bifurcation diagrams, Lyapunov exponent spectra, and attractor projections. Results confirm that the selected parameter region exhibits hyperchaotic behavior with high sensitivity to initial conditions and parameter perturbations. The effects of sensitivity, system dimension, and floating‐point precision on key space are systematically investigated and compared with conventional encryption standards. Simulation results show that at a sensitivity of 2 × 10 −16 , the key space reaches 7.812 × 10 109 , significantly exceeding the 1.158 × 10 7 7 of AES‐256. Increasing the system dimension from 4 to 7 further expands the key space. In addition, NIST SP 800–22 tests show P‐values above 0.01 and pass rates of 98%–100%, confirming the randomness of the generated key sequences. The proposed scheme provides an efficient and reliable solution for secure 6G communications.