الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Unlike encryption, Steganography hides existence of secret information rather than hiding its meaning only. Image based Steganography is the most common method used, since digital images are widely used over the Internet. However, the capacity is mostly limited and restricted by the size of cover images. In addition, there is a trade off between both Steganography capacity and stego image quality. Therefore, increasing Steganography capacity and enhancing stego image quality are still challenges. It exactly is the main aim of this research. The thesis investigates Steganography methods to achieve higher security levels for hiding secret information in communication systems. To get a high Steganography capacity and more imperceptibility; Steganography methods were proposed. The first proposal was based on spatial domain analysis by extending pixels format to increase capacity within cover image. Also, the quality of stego images was enhanced using fuzzy optimization to increase the stego image imperceptibility. More over, a trade-off factor was introduced to determine an optimum value for the Embedding Strength Factor (ESF) to get an acceptable visual vision. Also this work introduces a proposed idea”Denoising of Stego-images for different noise models” by using the hybrid domain which performed Stego-image and transmitted it through a noisy communication channel, so it is corrupted by existence of noise such as Gaussian noise, Salt&pepper noise and Speckle noise. To reduce the effect of these different types of noise, without Loss or damage edge details of Stego-image, is to use different filters whether Linear or nonlinear in the receiver such as Average filter, Wiener filter and Median filter. Experiments show that Mean Square Error (MSE), Peak Signal to Noise Ratio (PSNR), Correlation (COR) and Entropy are the most suitable assessment parameters that used as a quality and fidelity measures of stego images.Also, the thesis introduced ”A Proposed Implementation Method of an Audio Steganography Technique” that use the Least Significant Bit (LSB) technique to decomposed audio secret message in the audio cover and optimized the stego-data. In audio steganography; secret message is embedded in the digital sound by slightly altering the binary sequence of the sound file. Existing audio steganography software deal with WAV, AU, and even MP3 sound files. Embedding secret messages in the digital sound is usually a more difficult process than embedding messages in other forms, such as digital images. Audio steganography uses different algorithms, but least significant bit (LSB) is applied in this paper. The quality of sound depends on the size of the audio which the user selects and length of the message. Finally, the thesis introduced ” A denoising method For Secure Stego-images using AES for different noise models” that uses hybrid domain which combines both the spatial domain as well as the transform domain . Advanced Encryption Standard (AES) is used to encrypt the secret message and embedded it into the cover image to achieve greater robust, high security, hard to detect and more flexible.