الفهرس 
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Abstract
The fascinating developments of computer network technology during the last decade and the evolution of several applications like military image databases confidential video conferencing, medical imaging, cable TV, online personal photograph albums, etc. require reliable, fast and robust security systems to store and transmit digital images. Encryption of images is different from that of texts due to some intrinsic features of images such as bulk data capacity, high correlation among pixels and high
redundancy, which are generally difficult to handle by traditional methods Unfortunately, all traditional cryptosystems cannot fulfill all the requirements of
image encryption. In this thesis, three approaches are presented to adjust the traditional cryptosystems to fulfill the requirements of image encryption. We used the RC٦ and the Advanced Encryption Standard (AES) as examples of diffusion ciphers, and the chaotic Baker map as an example of permutation ciphers. These approaches are the homomorphic image encryption, chaotic encryption with different modes of operation,
and finally, an efficient diffusion mechanism for any cipher implemented in the electronic codebook mode (ECB). The homomorphic encryption can be used as a powerful diffusion mechanism Using modes of operation with the chaotic encryption increases the encryption quality and speed, and can be used to encrypt image with arbitrary dimensions. The diffusion mechanism presented in this thesis can be used to solve the encryption issues of the ECB mode without losing the advantage of parallel processing PDF created with pdfFactory trial version www.pdffactory.com