Exploitation des transformées paramétriques dans le cryptage des images fixes

Abstract

This work considers the encryption of images by exploiting the parametric transforms recently developed in the literature. The thesis firstly presents a literature review on image encryption techniques and a state of the art of parametric transforms and their development and construction methods. This literature review allowed us to develop two categories of new still image encryption methods by adopting the technique of block processing. The first category is mainly dedicated to the effective exploitation of complex-valued parametric transforms, including the reciprocal-orthogonal parametric (ROP) transform and the parametric discrete Fourier transform (DFT), whereas the second category is appropriate for real-valued parametric transforms, particularly the parametric discrete Hartley transform (DHT) and the ROP transform for the case of general real-valued parameters and the case of the parameters that are powers of two. The experimental results corresponding to security analysis, specifically the histogram analysis, objective measurements performed on the encrypted and decrypted images and the brute-force attack, obtained in this work clearly show the effectiveness and robustness of the methods proposed in this paper. In addition, these proposed methods have the advantage of reduced complexity compared to those of the existing image encryption methods.