Dual-Track Encryption Scheme for Ciphertext and Key Based on Dynamic Window Perturbation

This paper proposes a dual-track encryption scheme for ciphertext and key based on dynamic window perturbation, enabling highly secure information transmission in both the key and ciphertext dimensions. For key encryption, a modular exponentiation iteration algorithm is used to process the chaotic initial value key, which not only reduces the risk of key leakage but also expands the key space to 10⁹⁹. For ciphertext encryption, a three-dimensional Lorenz chaotic map is used to generate decision factors. Symbols are grouped according to dynamic window sizes, and each group is perturbed and encrypted based on the decision factors. The core advantage of the scheme lies in its symbol-level dynamic grouping encryption mechanism. Unlike traditional bit-level encryption, this scheme avoids the overhead of encrypting each symbol individually by applying dynamic window perturbation to symbol groups, reducing time costs by approximately 50% and more than doubling efficiency. In the 2 kilometer seven-core fiber experiment, the scheme achieved an encrypted signal transmission rate of 110.74 Gb/s, with all fiber cores meeting the hard-decision forward error correction (FEC) bit error rate (BER) threshold of 3.8 × 10⁻³. Experimental results demonstrate that even in cases of partial key leakage or key misalignment at an unauthorized receiver, the collaboration between the 10⁹⁹ key space and the dynamic window perturbation mechanism ensures both the security and processing efficiency of the communication system.