الفهرس 
Chapter 1Only 14 pages are availabe for public view
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Abstract
Image encryption is one prospective way to hide an image’s information. In addition, chaotic maps are distinguished by their unpredictability, bifurcation and acute susceptibility to initial conditions and parameters of control. As a result, chaotic systems are increasingly being used in recent image encryption studies, because the secret key should be volatile, unpredictable, and extremely sensitive to even little changes in value. The main goal of this thesis is to study the effect of some new smooth piecewise chaotic maps with different dimensions on improving image encryption by increasing the efficiency and security of the image encryption. To achieve this goal, we suggested three new encryption algorithms using chaotic maps, then we compared between them, and compared them with other algorithms in the literature. In an effort to obtain a higher level of security when encrypting images. The three suggested algorithms depend on the permutation-substitution model. This model is done in two steps: permutations (confusion) are used first to reduce the strong correlation between pixels and then substitution (diffusion) is made to modify the pixel value. Frist algorithm is based on non-chaotic random sequence generated by bisection method and chaotic random sequence generated by the Tent chaotic map. Second algorithm is based on a two-dimensional piecewise smooth nonlinear chaotic map. Third algorithm is based on a three-dimensional piecewise chaotic map. All three algorithms have been tested and compared with other algorithms in the literature. The results of histogram, information entropy analysis, correlation of adjacent pixels, NIST test established that all proposed algorithms can be used for image encryption efficiently. Through experimental analysis of key space, sensitivity analyses, noise attack analysis, and chosen plain-text attack analysis, it is proved that all proposed algorithms have a high level of resistance to avoid attacks by hackers.