Novel multiple-image encryption algorithm based on a two-dimensional hyperchaotic modular model

Current multiple-image encryption schemes usually require a fixed number or the same size of images. Therefore, this paper proposes a multiple-image encryption algorithm that can encrypt any number, size, and type of image. Firstly, we propose a two-dimensional chaotic model, which can generate multiple types of chaotic systems to solve the defects of some existing chaotic systems and reduce the design difficulty of chaotic systems. The generated chaotic systems are proven to have better performance through bifurcation diagrams, phase diagrams, Lyapunov exponent, and sample entropy analysis. Secondly, we fuse multiple images and then use SHA-512 to generate a secret key to increase resistance to plaintext attacks. We embed the size message of the original image into the fused image pixels, eliminating the need to transmit the size message separately from the secret key. Finally, we propose a simultaneous permutation and diffusion algorithm to improve security and efficiency. Experimental simulations and security analysis show that the proposed algorithm can encrypt multiple images of different sizes and types with good attack resistance and encryption efficiency.