A secure image encryption scheme using a newly constructed 4D chaotic system, reversible cellular automata, and DNA encoding operations

This work introduces a symmetric encryption framework designed to ensure secure transmission of grayscale images. The proposed cryptosystem combines a newly developed four-dimensional (4D) hyper chaotic system, a novel reversible cellular automaton, a new bit-level permutation strategy, DNA sequence operations, and the SHA-256 hash function. Unlike prior methods that use DNA coding only during encryption, the presented scheme employs SHA-256 together with DNA encoding/decoding and complementation rules to generate a cryptographically strong, large-scale key space. To overcome common weaknesses of existing chaotic maps-such as limited key space, simple dynamics, and non-uniform output distributions-a 4D chaotic generator (P4DCS) with a high Lyapunov exponent is proposed. Its structure draws from Ikeda, 2D Logistic, and several one-dimensional maps. Bit-level confusion is achieved by applying rotational shifts to rows and columns of the binary image matrix under the control of chaotic sequences. Specifically, the rows and columns within each segment of the binary matrix are reordered using chaotic sequences generated by the proposed 4D chaotic map. Diffusion is then performed using the reversible cellular automaton, whose rules and key are derived from the same chaotic system. Extensive security evaluations, including histogram analysis, entropy calculations, and correlation coefficient measurements, confirm the effectiveness of the method. The experimental results demonstrate strong resistance against statistical, differential, brute‑force, chosen-plaintext, noise, and data loss attacks, indicating that the proposed cryptosystem outperforms existing approaches in both security and reliability.