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UT Arlington EE 5359 - DIGITAL WATERMARKING

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DIGITAL WATERMARKING- Project Proposal ( EE 5359: Multimedia Processing )Under the guidance of, Dr. K. R. RaoSubmitted By,Ehsan [email protected] University of Texas at Arlington – Spring 2011DIGITAL WATERMARKINGIntroduction 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 iscalled digital watermarking.Digital watermarking is based on the science of steganography [2] or data hiding. Steganographycomes from the Greek meaning ‘covered writing’. Steganography is defined as the practice ofundetectably altering a work to embed a secret message. It is an area of research of communicating in ahidden manner. Steganography and watermarking rely on imperfections of human senses. The eyes and ears are notperfect detectors and cannot detect minor change therefore can be tricked into thinking two images orsounds are identical but actually differ, for example in luminance or frequency shift. The human eye hasa limited dynamic range so low quality images can be hidden within other high quality images [3]. Basic PrincipleThere are three main stages in the watermarking process [4]: - generation and embedding - attacks - retrieval/detectionGeneration of watermarks is an important stage of the process. Watermarks contain information thatmust be unique otherwise the owner cannot be uniquely identified. In embedding, an algorithm acceptsthe host and the data to be embedded and produces a watermarked signal. Various algorithms have beendeveloped so far [5-14].The watermarked signal is then transmitted or stored, usually transmitted toanother person. If this person makes a modification, this is called an attack. There are many possibleattacks. Detection is an algorithm which is applied to the attacked signal to attempt to extract thewatermark from it. If the signal is not modified during transmission, then the watermark is still presentand it can be extracted. If the signal is copied, then the information is also carried in the copy. Theembedding takes place by manipulating the contents of the digital data, which means the information isnot embedded in the frame around the data, it is carried with the signal itself. Figure 1 shows the basicblock diagram of watermarking process.Figure 1: Basic block diagram of watermarkingTypes of Watermarking:There are mainly three types of watermarking [15]:• Visible Watermarking• Invisible Watermarking• Dual watermarkingTechniques 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 imageEmbeddingWatermark ImageHost ImageWatermarked ImageExtractionPrivate KeyPrivate KeyExtracted watermark signal• Frequency domain: this technique is also called transform domain. Values of certain frequenciesare altered from their original. Spatial Domain:In this type of watermarking, the pixels of one or two randomly selected subsets of an image aremodified. These modifications can even include the flipping of the low-order bit of each pixel. But thistechnique 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 to an imageaccording to Iw(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 valueexceedsa threshold, watermark is detected.PatchworkThis algorithm has been proposed as an image watermarking scheme at the outset. This inserts theinformation into the time-domain signal. Original patchwork algorithm [20] is refreshingly novel amongmany watermarking methods. Moreover, the population of each subset was very large: It was not adaptiveto the signal: it added or subtracted constant d independently of the signal strength. Nonetheless, it hasprovided a solid base as an excellent tool for information hiding.Frequency DomainDiscrete 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 basicwavelets 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 GoalThis 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 andfollowed 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 theMSBs 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 BThe 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 20022. L.M. Marnel et al, “Spread spectrum image steganography”, IEEE Transactions on ImageProcessing, pp 1075-1083, Aug 19993. J.J.K O-Ruanaidh et al, “Watermarking digital images for copyright protection, IEE Proceedingsin Vision”, Image and Signal Processing, pp250-256, Aug 19964. I.


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UT Arlington EE 5359 - DIGITAL WATERMARKING

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