PowerPoint PresentationTable of ContentsProject ObjectivesWatermarking in GeneralSlide 5Slide 6Attacks on WatermarkSlide 8Slide 9Slide 10Slide 11Desired Characteristics of Invisible WatermarksSpread Spectrum WatermarkingSpread Spectrum Watermarking Insertion ProcessSpread Spectrum Watermarking Extraction ProcessExampleAdvantages & DisadvantagesConclusionReferences:Slide 20By Elo Leung and Wing WongCS 265 Section 2Spring 2004Table of Contents1. Project Objectives2. Watermarking in General3. Attacks on Watermarks4. Desired Characteristics of Invisible Watermarks5. Spread Spectrum Watermarking – Insert & Extract Watermark6. Example7. Advantages & Disadvantages8. ConclusionProject Objectives- Analyze the spread spectrum watermarking algorithm proposed by Cox et al.- Demonstrate the application of Cox’s algorithm using a sample image fileWatermarking in Generalthe 3 components:1. Watermark2. Encoder – watermark insertion3. Decoder and Comparator – watermark extraction and verificationWatermarking in Generalthe 3 components:1. Watermark2. Encoder3. Decoder and ComparatorEncoderOriginal WatermarkedImage (I ) Image (I' )Signature (S )EFigure provided by Mohanty [2].Watermarking in GeneralUses 3 components:1. Watermark2. Encoder3. Decoder and ComparatorDecoder Comp arat orTest Extracted match/Image (J ) Signature (S' )mismatch Origianal Image (I ) Origianal Signature (S )DCFigure provided by Mohanty [2].Attacks on Watermark TransmissionLossy OtherCompression International TamperingsProcessingII' Watermarked Object Corrupted Object TransmissionTypical Distortions and International TamperingGeometricalDistortionCommonSignalFigure provided by Cox et al. [1].Attacks on Watermark TransmissionLossy OtherCompression International TamperingsProcessingII' Watermarked Object Corrupted Object TransmissionTypical Distortions and International TamperingGeometricalDistortionCommonSignalIrreversible Data LossQuality Degradatione.g. JPEG/MPEGAttacks on Watermark TransmissionLossy OtherCompression International TamperingsProcessingII' Watermarked Object Corrupted Object TransmissionTypical Distortions and International TamperingGeometricalDistortionCommonSignalSpecific for images/videosrotation, translation, scaling, and cropping operationsAttacks on Watermark TransmissionLossy OtherCompression International TamperingsProcessingII' Watermarked Object Corrupted Object TransmissionTypical Distortions and International TamperingGeometricalDistortionCommonSignalanalog-to-digital, digital-to-analogconversion, etc.Attacks on Watermark TransmissionLossy OtherCompression International TamperingsProcessingII' Watermarked Object Corrupted Object TransmissionTypical Distortions and International TamperingGeometricalDistortionCommonSignalRewatermarkingDesired Characteristics of Invisible Watermarks1. Perceptually unnoticeable2. Robust to common watermark attacks3. Quality degradation upon removal of watermarks4. Unambiguously identifies the owner of the digitized medium (audio, video, or image).Spread Spectrum WatermarkingSpread Spectrum Watermark = Invisible WatermarkKey: • Insert watermark at perceptually significant regions• Spread watermark throughout the data **Data = audio, video, or image fileSpread Spectrum WatermarkingInsertion ProcessOriginal Image (V)SpectrumWatermark (X) Insert Modified Normally Distributed watermark SpectrumWatermarkedImage (V') Determine percetually significant regions Inverse FFT/DCTFFT/DCT Figure provided by Mohanty [2].v'i = vi (1 + αxi)Spread Spectrum WatermarkingExtraction ProcessRecoveredImage (I')RecoveredSpectrumOriginal FFT/ Original Image (V) DCT SpectrumExtractedWatermark (X*)does not similar? belongto owner yesbelongs toownernoOriginal Watermark (X) -Figure provided by Mohanty [2].sim(X, X*) = (X X*) sqrt (X X*)Example (1) Original (2) Watermarked Differences of (1) & (2)Advantages & DisadvantagesAdvantages:• Not noticeable since the watermarks are spread out.• Can’t be removed without severe quality degradation since watermarks are inserted at perceptually significant regions.Disadvantages:• Original watermark is required in the extraction process.ConclusionSpread spectrum watermarking:•Can be used for audio, video, and image files•Meets the desired characteristics of invisiblewatermarks – unnoticeable, robust, unambiguousReferences:[1]Ingemar J. Cox, et al., “Secure Spread Spectrum Watermarking for Multimedia”, IEEE Trans. on Image Processing, Vol. 6, No.12, Dec 1997, pp.1673-1687. [2] Saraju P. Mohanty, “Digital Watermarking: A Tutorial Review”, Department of Computer Science and Engineering, University of South Florida. [3] Peter Meerwald, “Digital Image Watermarking in the Wavelet Transform Domain”, Master’s Thesis, Department of Scientific Computing, University of Salzburg, Austria, January 2001.[4] http://www.cosy.sbg.ac.at/~pmeerw/Watermarking/source/The
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