Abstract
Securing digital images has become increasingly challenging due to the vast volume of images produced and transmitted across various platforms, coupled with the rising incidence of cybersecurity threats. Although attention has shifted toward utilizing hyperchaotic systems for image encryption, many cryptosystems that incorporate high-dimensional chaos along with other computationally intensive techniques face drawbacks, including speed limitations. Therefore, there is a pressing need for encryption schemes that are simple, fast, and sufficiently robust to meet the requirements of lightweight systems. This paper proposes a simple and efficient image encryption algorithm based on chaotic diffusion and random permutation. In this scheme, two low-dimensional chaotic systems are used to generate encryption keys, with one system being influenced by a SHA-256 hash value. The encryption process involves two rounds of chaotic diffusion interleaved with a random permutation to secure the images. The two distinct chaotic keystreams are applied at different stages of the encryption process to enhance randomness. Hashing is incorporated into keystream generation to ensure that the encryption key has a partial dependence on the image being encrypted. Pixel scrambling is performed mid-way by the permutation function to enhance randomness in the process. Experimental analyses, including key, differential, and statistical analyses, demonstrate that the proposed algorithm is fast, robust, and resistant to various types of security attacks on digital images.