الفهرس 
Chapter 1: Covert CommunicationOnly 14 pages are availabe for public view
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Abstract
Digital content, with the appearance of Internet and swift evolution of information technologies, has become an essential part of one’s day to day life. As it is easy to make an exact copy of the digital media, illegitimate sharing and replication of digital contents has become major concern for authors, publishers and legitimate owners of the contents. It has become imperative to keep the intellectual characteristics of digital content of a given media. In the beginning, ciphering and control access methods were used to protect from harm the authenticity of digital content of a given media. But this avoids free sharing and transmission of the content through the network, which is mostly not preferable to the author of the content. To deal with this problem, digital watermark technology has been appeared.
In this thesis, a new four methods in digital image watermarking which have a good PSNR, MSE and capacity, the proposed methods will be explained, discussed and evaluated in the following chapters of this thesis.
The first proposed method is called SLDIP (Substitute Last Digit in Pixels) method, which consists of two algorithms, one for watermark embedding and other for watermark extraction. The embedding algorithm has been done based on insertion of the watermark in the last digit in each pixel of the cover image. Also the extraction algorithm has been done based on collecting last digits of each pixel in the watermarked image to result the watermark. SLDIP has better results, in addition the larger watermark capacity which SLDIP can embed in cover image.
The second proposed method is called MSLDIP (Modified Substitute Last Digit in Pixels) method, which is same as SLDIP but with some modifications in embedding process. The embedding algorithm has been also done based on SLDIP embedding but with simple modification that increase the PSNR value of the watermarked image. MSLDIP has better results than SLDIP, in addition the larger watermark capacity which also MSLDIP can embed in cover image.
The third proposed method is called modified MSLDIP method, Modified MSLDIP is a modification on MSLDIP by performing RC4 (Rivest Cipher 4) encryption operation on the watermark before the embedding process, and also in the extraction process the output will be the encrypted watermark which must be decrypted using RC4 decryption operation to output the original watermark. Modified MSLDIP has results approximately equal to results of the MSLDIP method but in the Modified MSLDIP the watermark will be secured, and it has larger watermark capacity.
The fourth proposed method is called PRNG Based MSDLIP (Pseudo-Random Number Generator Based Modified Substitute Last Digit in Pixels) method, this method is a modification of the previous method (Modified MSLDIP) where the embedding process has been done based on PRNG locations. The results were slightly better than Modified MSLDIP, the watermark will be more secured and large capacity in the cover image.