Hyperchaos-Driven 3D RGB Image Scrambling and Encryption for Multi-Image Security

초록

In today's digital era, images play a vital role across diverse fields, including healthcare, banking, defence, traffic monitoring, and weather forecasting. As digital footprints, their use is rapidly growing, but they are also increasingly vulnerable to unauthorised access and misuse. To address this challenge, we propose a novel encryption scheme for multiple red, green, blue (RGB) images. The scheme takes an arbitrary number of images, overlays them to form a three-dimensional (3D) image, and then divides it into four subparts. A five-dimensional multi-wing hyperchaotic map is employed for random selection of parts, images, rows, columns, and key images. Rows and columns from selected images are repeatedly swapped to produce scrambled 3D images, which are further XORed to generate the final encrypted outputs. The encrypted images are then combined into a large 3D RGB cipher image. To enhance security, the scheme integrates a 256-bit salt key with SHA-256 hash codes, ensuring strong key space and plaintext sensitivity. Experimental results demonstrate that the proposed approach provides robustness against multiple threats, real-world applicability, and high security. Notably, the scheme achieved a highly competitive information entropy value of 7.99994, confirming its effectiveness. Extensive experiments further show that the ciphertexts exhibit high randomness and robustness: average correlation coefficients (CCs) between adjacent pixels are close to zero, the number of pixel change rate is 99.63%, and the unified average changing intensity is 33.45%. The decrypted images achieve peak signal-to-noise ratio (PSNR) values of infinity (O-D) and 7.9982 (O-C), confirming lossless reconstruction. Moreover, the scheme demonstrates strong resistance to chosen plaintext as well as noise and cropping attacks, while maintaining competitive computational efficiency. Comparative analysis with recent chaos-based algorithms verifies that the proposed approach provides superior security, randomness, and robustness for secure image transmission.

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