Dynamic window-based image encryption algorithm driven by a state-adaptive delayed chaotic system
Bocheng Liu, Niande Jiang, Zanxing Huang, Jian Song, Jiayu Deng, Lingfeng Liu · Journal of King Saud University - Computer and Information Sciences · 2026
Digital images usually contain large data volumes, high redundancy, and strong adjacent-pixel correlations, which impose high requirements on encryption security and diffusion performance. To address the dynamical degradation of low-dimensional chaotic systems under finite-precision implementation and the insufficient perturbation propagation caused by fixed-block diffusion, this paper proposes a plaintext-related image encryption scheme driven by a four-dimensional state-adaptive delayed chaotic system. The constructed 4D-SAD system integrates Logistic, Sine, Cubic, and Tent maps through a ring-type delayed coupling structure, introduces an amplified modulo-folding factor to strengthen the stretching-and-folding behavior of the chaotic source, and employs a state-adaptive delay function to make historical-state access dynamically determined by the current system state. Based on this system, a bidirectional dynamic-window encryption framework is designed. The plaintext hash and a session nonce are jointly used for session-key derivation, while Fisher–Yates global permutation, Bit-Swap bit-level perturbation, bidirectional dynamic-window diffusion, and global correction are combined to achieve image encryption. Experimental results demonstrate that the proposed scheme can generate chaotic sequences with improved dynamical randomness, effectively conceal plaintext information, reduce pixel correlations, enhance differential diffusion, and provide good key sensitivity and reversibility.