Multiple-Image Encryption Using Sine Quadratic Polynomial Mapping and U-Shaped Scanning Techniques

In the realm of digital image security, the multiple-image encryption (MIE) has garnered increasing attention due to the prevalent dissemination of digital imagery.Responding to this trend, an innovative encryption method has been developed, capable of securing an arbitrary number of images efficiently.This method is underpinned by the newly devised sine quadratic polynomial map (SQPM) and an original space-filling curve technique, termed U-shaped scanning.Extensive analysis, including 2D and 3D phase diagrams, Lyapunov exponents, bifurcation diagrams, and approximate entropy calculations, confirms the SQPM's chaotic properties over a broad spectrum of control parameters.The U-shaped scanning method, novel in its application, facilitates the traversal of every element in a 2D array, irrespective of its dimensions.This method is integral to the permutation phase of the encryption process, where it pre-scrambles input images, and it plays a pivotal role in the diffusion phase through the introduction of U-shaped diffusion.Comprehensive security assessments have been conducted, encompassing secret key analysis, histogram evaluation, correlation assessments, differential analysis, and information entropy measurements.Further scrutiny involves known-plaintext and chosen-plaintext attack resilience, along with visualizations of data loss and noise attack impacts, and execution time analysis across three sets of four images.The results of these security analyses affirm the efficacy of the proposed technique in encrypting multiple images, be they colored or grayscale.This work not only advances the field of image encryption but also introduces novel methodologies with broad applicability in digital image security.