Variable-order QNSC with turbulence-induced perturbation for LEO-to-Earth secure laser communication

This paper proposes a turbulence-induced perturbation (TIP) approach to address the security degradation of quantum noise stream cipher (QNSC) systems under high transmit power and introduces a variable-order quantum noise stream cipher (VO-QNSC) scheme to further enhance transmission performance. The TIP approach incorporates turbulence-induced perturbation to strengthen the physical-layer security of QNSC in high-power scenarios, while the VO-QNSC scheme significantly improves system performance without increasing algorithmic complexity or redundancy, making it suitable for deployment on satellite terminals with limited computational resources. Simulation results show that, after introducing TIP, the system detection failure probability (DFP) can exceed 99.97% and number of masked signals (NMS) is improved to the order of 10³, which effectively enhances the anti-eavesdropping ability of the system. For poor channel conditions, VO-QNSC can improve the receiver sensitivity by up to approximately 0.5 dB, which can meet the requirements of communication security and transmission performance in complex environments.