A colour image encryption method based on a coupled map lattice–elementary cellular automaton neurodynamic chaotic system and dynamic dual-affine substitution-box architecture

Abstract

Abstract Secure colour image transmission requires encryption schemes in which randomness generation, nonlinear substitution and diffusion are designed as a coherent whole. Conventional coupled map lattice-based methods are often constrained by fixed neighbourhood evolution and limited coupling diversity, while many chaos-based substitution-box (S-box) schemes use chaotic sequences mainly as external shuffling sources. This article develops a colour image encryption method that couples adaptive spatio-temporal chaos with dynamic finite-field substitution and coordinated permutation–diffusion. In the proposed chaotic model, lattice interactions and local evolution are regulated by the system state, allowing the generated sequences to exhibit stronger complexity, sensitivity and distribution uniformity. The resulting chaotic flow is further embedded into a dual-affine construction over GF(28), producing key-dependent bijective S-boxes with enhanced nonlinear substitution capability. For image encryption, time-varying bit-switching transform (TV-BST) permutation, Hopfield-driven time-varying coupled map lattice (HDTCML) block key mixing and dynamic S-box-based bidirectional diffusion are integrated to jointly strengthen global scrambling, local confusion and plaintext sensitivity. Experimental analyses show that the proposed scheme produces random-like ciphertexts, suppresses adjacent-pixel correlation and improves resistance to statistical analysis, differential attacks and chosen-plaintext attacks.