A color image encryption method integrating exponential embedded spatiotemporal chaos and laplacian modulation

As digital images are widely transmitted, stored, and processed in digital communication systems, the security of image information is now a major issue. Owing to its the sensitivity to initial conditions and pseudo-random behavior of chaotic systems, chaotic encryption has become an active field of research. Nevertheless, many existing chaotic encryption methods still suffer from limited chaotic ranges, weak plaintext sensitivity, or insufficient diffusion capability. To address these issues, this work presents a three-stage cascade color image encryption algorithm using an improved spatiotemporal chaotic system. First, a 1D exponential-embedded sine map (1D-EESM) is designed and further embedded into a coupled map lattice. Bifurcation diagrams, information entropy and Kolmogorov-Sinai entropy analyses demonstrate that the EESMCML exhibits stronger spatiotemporal chaos intensity and sequence randomness. Second, a three-layer encryption framework consisting of Perturbation-Scrambling-Diffusion is proposed. Specifically, the Chaotic Exponential Initial Perturbation Algorithm (CEIPA) is first applied using the 1D-EESM. Then, a threedimensional index matrix is constructed with the EESMCML to simultaneously perform double scrambling of pixel spatial positions and RGB channels. Finally, the Laplacian Feature-Modulated Diffusion (LFMD) is introduced, employing a forwardbackward bidirectional structure to achieve global adaptive pixel confusion. As demonstrated by experiments, the proposed method offers favorable security performance and withstands differential, chosen-plaintext, cropping and noise attacks.