RMIE-CSCA-RPD: a robust multiround image encryption scheme using chaotic systems and cellular automata in a rewriting–permutation–diffusion framework

We introduce RMIE-CSCA-RPD, a multiround symmetric image encryption scheme specifically designed to enhance security. The approach integrates multichaotic maps and cellular automata (CA) within a rewriting–permutation–diffusion model. The encryption process begins with an initial transformation of pixel values, followed by multiple rounds of confusion. This confusion is achieved through circular row- and column-wise shifts and inter-sub-image exchanges. Both operations are dynamically controlled by the Hénon chaotic map, with sub-images formed by dividing an M×N image into four equal M/2×N/2 sub-images. A unique permutation sequence is generated using a combination of the plain image and an external 64 byte secret key, making the process highly sensitive to input changes. For robust pixel-level diffusion, a subsequent stage employs a diffusion key derived from the secret key. This key leverages CA and the Lorenz chaotic map, which is precisely solved using the fourth-order Runge–Kutta method. The proposed scheme demonstrates strong resilience against cryptanalytic attacks and benefits from an extensive key space of 2512. Comprehensive statistical analyses, including the number of pixel changing rate, unified average changing intensity, entropy, correlation, mean square error, peak signal-to-noise ratio, mean absolute error, and National Institute of Standards and Technology tests, consistently confirm the scheme’s robustness, enhanced security, and computational efficiency across images of varying sizes. Comparative assessments with existing encryption techniques further highlight its effectiveness.