DIGITAL WATERMARKING Project Proposal EE 5359 Multimedia Processing Under the guidance of Dr K R Rao Submitted By Ehsan Syed 1000671971 seaquadri gmail com The University of Texas at Arlington Spring 2011 DIGITAL WATERMARKING Introduction Watermarking is defined as the practice of altering a work to embed a message about that work 1 Embedding a digital signal audio video or image with information which cannot be removed easily is called digital watermarking Digital watermarking is based on the science of steganography 2 or data hiding Steganography comes from the Greek meaning covered writing Steganography is defined as the practice of undetectably altering a work to embed a secret message It is an area of research of communicating in a hidden manner Steganography and watermarking rely on imperfections of human senses The eyes and ears are not perfect detectors and cannot detect minor change therefore can be tricked into thinking two images or sounds are identical but actually differ for example in luminance or frequency shift The human eye has a limited dynamic range so low quality images can be hidden within other high quality images 3 Basic Principle There are three main stages in the watermarking process 4 generation and embedding attacks retrieval detection Generation of watermarks is an important stage of the process Watermarks contain information that must be unique otherwise the owner cannot be uniquely identified In embedding an algorithm accepts the host and the data to be embedded and produces a watermarked signal Various algorithms have been developed so far 5 14 The watermarked signal is then transmitted or stored usually transmitted to another person If this person makes a modification this is called an attack There are many possible attacks Detection is an algorithm which is applied to the attacked signal to attempt to extract the watermark from it If the signal is not modified during transmission then the watermark is still present and it can be extracted If the signal is copied then the information is also carried in the copy The embedding takes place by manipulating the contents of the digital data which means the information is not embedded in the frame around the data it is carried with the signal itself Figure 1 shows the basic block diagram of watermarking process Watermark Image Private Key Embedding Host Image Extracted watermark signal Watermarked Image Private Key Extraction Figure 1 Basic block diagram of watermarking Types of Watermarking There are mainly three types of watermarking 15 Visible Watermarking Invisible Watermarking Dual watermarking Techniques of Watermarking There are mainly two major techniques of watermarking 16 Spatial domain slightly modifies the pixels of one or two randomly selected subsets of an image Frequency domain this technique is also called transform domain Values of certain frequencies are altered from their original Spatial Domain In this type of watermarking the pixels of one or two randomly selected subsets of an image are modified These modifications can even include the flipping of the low order bit of each pixel But this technique is not considered reliable for normal media operations like lossy compression or filtering 9 LSB Coding The least significant bits of the host signals are modified by the watermark signal Correlation Based Pseudo random noise PN with a pattern W x y is added according to to an image I w x y I x y K W x y At the decoder the correlation between the random noise and the image is found If the value exceeds a threshold watermark is detected Patchwork This algorithm has been proposed as an image watermarking scheme at the outset This inserts the information into the time domain signal Original patchwork algorithm 20 is refreshingly novel among many watermarking methods Moreover the population of each subset was very large It was not adaptive to the signal it added or subtracted constant d independently of the signal strength Nonetheless it has provided a solid base as an excellent tool for information hiding Frequency Domain Discrete Cosine Transform DCT The sequence of data points in the spatial domain are converted to the sum of sine and cosine waveforms with different amplitudes in the frequency domain Unlike Discrete Fourier Transform this transform has only real numbers when a cosine function is used There are eight different variants of DCT with slight modifications between them 17 18 19 Discrete Wavelet Transform DWT In this transform the signal is decomposed into a set of basic wavelets followed by the altering of lower frequencies at various resolutions 17 18 19 For this project a form of spatial domain watermarking technique will be used Project Goal This project aims at embedding a watermark into an image using a form of spatial domain technique which is least significant bit technique and then performing JPEG compression and decompression and followed by the removal of watermark from the watermarked image The following are the subdivisions of the project Embedding the Watermark image into the Host image Host image A is selected A watermark image B is selected The least significant bits LSBs of the host image A will be replaced by the most significant bits MSBs of the watermark image B A watermarked image C is obtained which contains the image A with its LSBs replaced by the MSBs of B Compression of the watermarked image Watermarked image C is read Discrete Cosine Transform is applied 21 22 Block is compressed through quantization or Huffman coding Decompression of the watermarked image The compressed image will now be decompressed Removing the watermark from the watermarked image The watermark from the watermarked image C is removed It gives host image A and the watermark image B The tools used in this project s implementation are MATLAB Visual Studio References 1 I Cox et al Digital Watermarking Journal of Electronic Imaging Vol 11 No 3 July 2002 2 L M Marnel et al Spread spectrum image steganography IEEE Transactions on Image Processing pp 1075 1083 Aug 1999 3 J J K O Ruanaidh et al Watermarking digital images for copyright protection IEE Proceedings in Vision Image and Signal Processing pp250 256 Aug 1996 4 I J Cox and M L Miller A review of watermarking and the importance of perceptual modeling Proceedings of Electronic Imaging February 1997 5 H J Wang et al Wavelet based digital image watermarking Optics Express PP 491 496 Dec 1998 6 P T Yu et al Digital watermarking based on
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