Parallel Bit-Level Image Encryption Using a Two-Dimensional Sine-Coupled Map and Josephus Scrambling

Khaled El Hadad; Salah Abokhatwa

doi:10.69667/ajs.26904

Authors

Khaled El Hadad Faculty of Engineering, Garaboulli, Elmergib University, Libya Author https://orcid.org/0000-0002-0374-4350
Salah Abokhatwa Faculty of Engineering, Garaboulli, Elmergib University, Libya Author https://orcid.org/0009-0006-3897-4718

DOI:

https://doi.org/10.69667/ajs.26904

Keywords:

Image Encryption, Two-Dimensional Chaotic Map, Bit-Level Permutation, Josephus Traversal, SHA-256

Abstract

This paper presents a parallel bit-level image-encryption scheme based on a two-dimensional sine-coupled chaotic map, a plaintext-dependent SHA-256 key-derivation step, Josephus-based bit scrambling, and feedback diffusion. The image is divided into high- and low-order bit groups, which are scrambled using chaotic sequences before recombination and diffusion. Tests on three grayscale benchmark images produced ciphertext entropy above 7.9990, absolute adjacent-pixel correlation below 0.002, NPCR values from 99.5995% to 99.6116%, and UACI values from 33.4327% to 33.5168%. The reported implementation encrypted a 256 × 256 image in approximately 0.04 s. These results indicate good statistical diffusion and support further evaluation of the scheme for resource-constrained image-transmission applications.