Color image encryption algorithm using a new four-dimensional hyperchaotic system

With the widespread applications of digital images in fields such as medical imaging, remote sensing, and financial transactions, ensuring image confidentiality has become increasingly important. However, some existing image encryption schemes still suffer from limited key space and insufficient security. To address these, this paper proposes a novel color image encryption algorithm (CIEA-4DALHS) based on a newly constructed four-dimensional augmented Lü hyperchaotic system (4DALHS). The scheme integrates bidirectional spiral cross scrambling with arbitrary starting points and four traversal modes, bit-plane substitution for fine-grained pixel modification, and hierarchical regional segmentation diffusion with cross-channel cascading effects. These strategies significantly enhance both permutation and diffusion effects. Experimental results and security analysis demonstrate the superiority of CIEA-4DALHS. For example, the key space is sufficiently large, high ciphertext information entropy, and strong robustness against statistical and differential attacks. Compared with recent methods, the proposed scheme CIEA-4DALHS offers both high efficiency and security, highlighting its strong potential for real-world applications in image protection.