الفهرس 
AbstractOnly 14 pages are availabe for public view
 |  | from | 107 |  |  |
| | | from | 107 | | |
Abstract
In recent years, the problem of prohibited data processing and the exchange of digital data has become increasingly severe with the rapid growth of information communication technology and Internet applications. Therefore it was very important to make all effort to secure and encrypt the data against various types of attacks. Encryption techniques have appeared as effective practical tools in validating and securing information. Most of traditional techniques suffer from more than one weakness point. Color images are a very important and vital type of multimedia. In this thesis, three encryption techniques have been proposed to secure the color image against various types of attacks as follows; (i) chaos based encryption technique, (ii) chaos based hybrid encryption and watermarking technique, and (iii) chaos based hybrid encryption, steganography and watermarking technique. In encryption technique the image could be converted into an encrypted form using a secret key that has been represented by various chaotic maps. In watermarking technique the signature is embedded in a digital image. In Steganography technique the original image is concealed in the cover image to masquerade the hacker and the output image called stego image. The performance of these techniques will be compared to the performance of the traditional ones for color image against severe composite attacks. The main challenge was to get high robustness against composite attacks, in which three various types of attacks have been merged; noise, rotation and cropping attacks. This composite form of attacks could be imposed to the encrypted image (friendly form) or to the original one (hard form). Eight performance metrics have been used for measuring the performance against these forms of attacks. After extensive studies it has been found that the proposed techniques have achieved the best performance and have given better robustness against composite attacks than that of the traditional ones. Six chaotic maps have been used to establish the data encryption with different parameters. High performance enhancement ratios against composite types of attacks have been achieved by using the proposed algorithms.