Hasslacher Digital Watermarking
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Transcript of Hasslacher Digital Watermarking
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DigitalDigital WatermarkingWatermarking
Alexander Hasslacher, 0056448Alexander Hasslacher, 0056448
EMTEMT--InstitutInstitut,, JKUJKU--LinzLinz, 2004, 2004
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WhatWhat
isis
aa
WatermarkWatermark
EncoderOriginal Image (I)
Signatur (S)
Watermarked Image (I)
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TypesTypes of Digitalof Digital WatermarksWatermarks
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VisibleVisible
andand
invisibleinvisible
WatermarkWatermark
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LSBLSB
forfor
*.BMP*.BMP
LSBLSB
00100111 11101001 1100100000100111 11101001 11001000
00100111 11001000 1110100100100111 11001000 11101001
11001000 00100111 1110100111001000 00100111 11101001
Hide a binary value for A 10000011Hide a binary value for A 10000011 00100111 111010000100111 111010000 1100100011001000 0010011001001100 11001000 111010011001000 111010000
11001000 00100111 1110100111001000 00100111 11101001
fragile against noise & compressionfragile against noise & compression
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FFT, DCTFFT, DCT
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DCT Domain WatermarkingDCT Domain Watermarking
Watermark embeddingWatermark embedding W: watermark to be embedded.W: watermark to be embedded. X: sequence of pixel valuesX: sequence of pixel values
XXdd and Yand Ydd: row: row--concatenated DCT coefficients of X and Yconcatenated DCT coefficients of X and Y A=scaling factor: Determines the intensity of the watermarkA=scaling factor: Determines the intensity of the watermark
YYdd(i(i) = X) = Xdd(i)(1+aW)(i)(1+aW)
Watermark extractionWatermark extraction W*: extracted version of the watermarkW*: extracted version of the watermark ZZdd: possibly forged watermarked image.: possibly forged watermarked image.
T=userT=user--defined thresholddefined threshold If S > T, image is authenticIf S > T, image is authentic
*
***
*
*),(1
)(
)(1)(
WW
WWWWS
iX
iZ
a
iW
d
d===>=
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ConclusionsConclusions Modification ofModification ofallall DCT coefficients distorts the imageDCT coefficients distorts the image
drasticallydrastically
TheThe scaling factorscaling factor a is a critical system parameter.a is a critical system parameter. If a is tooIf a is too smallsmall. The image is not distorted but the robustness. The image is not distorted but the robustnessof the scheme is lowof the scheme is low
If a is tooIf a is too largelarge, the image is distorted but the robustness of the, the image is distorted but the robustness of the
scheme is highscheme is high Modification ofModification oflowlow--frequencyfrequency coefficientscoefficients Distorts the imageDistorts the image Gives the hacker a clue about where the watermark isGives the hacker a clue about where the watermark is
embeddedembedded Modification ofModification ofhighhigh--frequencyfrequency coefficientscoefficients
No distortionNo distortion TheThe watermakrwatermakr cannot be detected after attacks like JPEGcannot be detected after attacks like JPEG
compressioncompression
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ExamplesExamples InvisibleInvisible WatermarkingWatermarking
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ExampleExample 22 InvisibleInvisible WMWM
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VisibleVisible WatermarkingWatermarking
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BothBoth,, InvisibleInvisible andandVisibleVisible WMWM
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AttacksAttacks on WMon WM
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Audio WatermarkingAudio Watermarking
UsesUses DRM (Digital RightDRM (Digital Right ManamementManamement))
Proof of ownershipProof of ownership
Access control for digital mediaAccess control for digital media Tracing illegal copies Tracing illegal copies
Transmitting MetadataTransmitting Metadata
Like composer, soloist, genre of music,Like composer, soloist, genre of music,
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AudioAudio WatermarkingWatermarking
RequirementsRequirements Hidden, in case of music inaudibleHidden, in case of music inaudible
Statistically invisibleStatistically invisible
Robust against signal processing operationsRobust against signal processing operations
Directly connected to the music, not in aDirectly connected to the music, not in a
headerheader Key dependentKey dependent
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InaudibleInaudible Signals in Audio WMSignals in Audio WM
Temporal maskingTemporal masking 55--20ms before a loud signal20ms before a loud signal 5050--200ms after a loud signal200ms after a loud signal
A silent sound after a loud soundA silent sound after a loud sound Adding a echoAdding a echo
0 = 0.5ms after a sound0 = 0.5ms after a sound
1 = 1.0ms after a sound1 = 1.0ms after a sound MP3StegoMP3Stego
WAVWAV --> MPEG> MPEG--3 + additional Data3 + additional Data
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MP3StegoMP3Stego
Versteckter Text: Dies ist Alex sein File
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i.Ei.E:: GoogleGoogle ImagesearchImagesearch
WebcrawlerWebcrawler looking for Watermarkedlooking for Watermarkedpictures on Homepagespictures on Homepages
Money for PhotographersMoney for Photographers
MicrosoftsMicrosofts picturetankpicturetank
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QuestionsQuestions ??
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ThanksThanks forfor comingcoming!!!!