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Digital Image Watermarking Department of E & C, SJCE, Mysore Page 1 ABSTRACT Digital watermarking is a promising solution for content copyright protection in the global network. It imposes extra robustness on embedded information. Digital watermarking is the science of embedding copyright information in the original files. The information embedded is called watermark. This report deals with the implementation of digital watermarking on images in spatial and frequency domain. LSB substitution algorithm is used for implementation in spatial domain whereas Cox’s method is used for implementation in frequency domain.
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Digital Image Watermarking Department of E & C, SJCE, MysorePage 1 ABSTRACT Digitalwatermarkingisapromisingsolutionforcontentcopyrightprotectioninthe global network. It imposes extra robustness on embedded information. Digital watermarking is the science of embedding copyright information in the original files. The information embedded is called watermark. This report deals with the implementation of digital watermarking on images in spatial and frequency domain. LSB substitution algorithm is used for implementation in spatial domain whereas Coxs method is used for implementation in frequency domain. Digital Image Watermarking Department of E & C, SJCE, MysorePage 2 CHAPTER 1 INTRODUCTION 1.1 The Need For Watermarking One of the most important properties of digital information is that it is in principle very easy to produce and distribute unlimited number of its copies. This might undermine the music, film,bookandsoftwareindustriesandthereforeitbringsavarietyofimportantproblems concerningtheprotectionoftheintellectualandproductionrightsthatbadlyneedtobe solved. The fact that an unlimited number of perfect copies of text, audio and video data can be illegally produced and distributed requires studying ways of embedding copyright information and serial numbers in audio and video data. This is where the concept of watermarking comes into the picture. Digital watermarking is the process of inserting a digital signal or pattern into digital content. The signal, known as a watermark, can be used later to identify the owner of the work, to authenticate the content, and to trace illegal copies of the work. There are a variety of image watermarking techniques, falling into 2 main categories, depending on in which domain the watermark is constructed spatial and frequency domain. Image watermarking techniques that take advantage of properties of the human visual system, and the characteristics of the image create the most robust and transparent watermarks.

1.2 Brief History Of Digital Watermarking It is difficult to determine when digital watermarking was first discussed. In 1954, Emil Hembrooke of the Muzak Corporation filed a patent for watermarking his musical works. Komatsu and Tominaga, in 1988, appear to have first used the term digital watermark. The CopyProtectionTechnicalWorkingGroup(CPTWG)testedwatermarkingsystemsfor protection of video on DVD disks. The International Organization for Standardization (ISO) took an interest in the technology in the context of designing advanced MPEG standards. Inthe area of image watermarking, Digimarc bundledits watermark embedder and detectors with AdobesPhotoshop.Morerecently,anumberof companieshaveusedwatermarking technologies for a variety of applications. Digital Image Watermarking Department of E & C, SJCE, MysorePage 3 CHAPTER 2 GOALS AND OBJECTIVES OF WATERMARKING 2.1 Criteria To Be Satisfied To be effective in the protection of the ownership of intellectual property, the invisibly watermarked document should satisfy several criteria:Thewatermarkmustbedifficultorimpossibletoremove,atleastwithoutvisibly degrading the original image. The watermark must survive image modifications that are common to typical image-processingapplications(e.g.,scaling,colorrequantization,dithering,cropping,and image compression).An invisible watermark should be imperceptible so as not to affect the experience of viewing the image.For some invisible watermarking applications, watermarks should be readily detectable bytheproperauthorities,evenifimperceptibletotheaverageobserver.Such decodability without requiring the recovery of property and subsequent prosecution. 2.2 Features Of Digital Watermarking:Thedigitalwatermarkingtechniqueisappealing,sinceitprovidesfollowingmain features: 2.2.1 Robustness:Depending on the application, the digital watermarking technique can support different levels of robustness against changes made to the watermarked content.If digital watermarking is used for ownership identification, then the watermark has to be robust against any modifications. The watermarks should not get degraded or destroyed as a result of unintentional or malicious signal and geometric distortions like A/D conversion, D/A conversion, cropping, re-sampling, rotation, dithering, quantization, scaling and compression of the content.Ontheotherhand,ifdigitalwatermarkingisusedforcontentauthentication,the watermarks should be fragile, i.e., the watermarks should get destroyed whenever the content is modified so that any modification to content can be detected. Digital Image Watermarking Department of E & C, SJCE, MysorePage 4 2.2.2 Inseparability:After the digital content is embedded with watermark, separating the content from the watermark to retrieve the original content is not possible. 2.2.3 Security:Thedigitalwatermarkingtechniquespreventunauthorizedusersfromdetectingand modifyingthewatermarkembeddedinthecoversignal.Watermarkkeysensurethatonly authorized users are able to detect/modify the watermark. 2.2.4 Effect On Bandwidth:Watermarking should be donein such a way that it doesnt increase the bandwidth required for transmission. If Watermarking becomes a burden for the available bandwidth, the method will be rejected. CHAPTER 3 APPLICATIONS Digitalwatermarkingtechniqueshavewiderangingapplications.Someofthe applications are enlisted below.Copyright Protection: Digital watermarks can be used to identify and protect copyright ownership.Digitalcontentcanbeembeddedwithwatermarksdepictingmetadata identifying the copyright owners.CopyProtection:Digitalcontentcanbewatermarkedtoindicatethatthecontent cannotbeillegallyreplicated.Devicescapableofreplicationcanthendetectsuch watermarks and prevent unauthorized replication of the content.Broadcast Monitoring: Digital watermarks can be used to monitor broadcasted content like television and broadcast radio signals. Advertising companies can use systems that candetectthebroadcastofadvertisementsforbillingpurposesbyidentifyingthe watermarks broadcast along with the content.ConcealedCommunication:Sincewatermarkingisaspecialtechniqueof steganography, it can be used for concealed communication also. Digital Image Watermarking Department of E & C, SJCE, MysorePage 5 CHAPTER 4 WATERMARKING IMPLEMENTATION 4.1 Approach: There are two parts to building a strong watermark. The watermark structure The insertion strategy In order for a watermark to be robust and secure, these two must be designed correctly.In this project, we have implemented the digital watermarking usingLeast Significant Bit (LSB) substitution algorithm (Spatial domain) Cox method using DCT (transform domain) 4.1.1 LSB Substitution Algorithm Using LSB manipulation, very large amount of information can be hidden with very little impact to image quality. This is performed in spatial domain. The embedding of watermark is performed choosing a subset of image pixels and substituting the LSB of each of the chosen pixels with watermark bits.Extraction of watermark is performed by extracting LSB of each of the selected image pixels. If the extracted bits match the inserted bits then the watermark is detected. The LSB substitution algorithm can be represented in the form of an equation as a =x ( b / y ) +c / z Where 'a' is the watermarked image, 'b' is the cover image, 'c' is the watermark and x, y and z are integers that decide the amount of watermark to be applied and 0