一种稳健的基于小波变换的彩色图像数字水印算法.docx

一种稳健的基于小波变换的彩色图像数字水印算法.docx

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一种稳健的基于小波变换的彩色图像数字水印算法

I

ABSTRACT

Therevolutionofthedigitalinformationhasbroughtbigchangesinourlivesandour

society.Thedigitalinformationhasalsogeneratednewchallengesandnewopportunities

forinnovation.Thisthesisdiscussestheissuesregardinginformationhidinginthedigital

imageanditsapplicationforsecurethedigitalmultimedia,addressingboththeoretical

andpracticalaspectsandtackingbothdesignandattackproblems.Inthefundamental

part,wediscussthekeyelementsofwatermarkinganditsapplicationindigitalimage.In

thedesignpart,wepresentnewinformationhidingalgorithmfordigitalcolorimage.The

designprovidesconcreteexamplesregardingthechoiceofembeddingandextraction

mechanisms.Withthegrowthofnetworkedmultimediasystems,theneedofsecure

communicationanddatatransfergoincreasingly.Applicationsarenumerousandvarious

likesatelliteormedicalimagery,orremotemonitoring.Duringimagestransfer,data

integrityisnotreallysecure.Watermarkingcanbeananswertosuchproblems.Inthis

paper,Arobustwavelet-basedcolorimagedigitalwatermarkingschemeisproposed.The

proposeddigitalwatermarkisarandomrealnumberofasequenceofbitsembeddinginto

lowfrequencyofGreencomponentsub-band.Theembeddingmethodisbasedonthree

levelsDiscreteWaveletTransform（DWT）lowcoefficient.Athresholdisusedto

generatefrequencyofwatermarkswiththecompareofcreatedfrequencyofDWTin

embeddingposition.Experimentalresultsshowedthattheembeddedwatermarkisrobust

againstvarioussignalprocessingandcompressionattackssuchasSalt&peppernoise

addition,Cropping,Scaling,JPEGcompression,Meanfiltering,Copyingandpastingand

soon.

Keywords:

Digitalwatermarking,wavelettransform,Colorimage,Greencomponent,

LowfrequencyandRobustness,informationhiding.

3

ListofFigures

Figure2.10.1Schematicdescriptionofsteganography………………………………..5

Figure:

2.2Communicationchannelforcryptosystem…………………………………7

Figure2.3MonogramsfiguringTGERG……………………………………………….8

Figure2.4Genericdigitalwatermarkingscheme………………………………………11

Figure2.5Genericdigitalwatermarkingdecoder……………………………………..11

Figure2.6Genericdigitalwatermarkingscheme………………………………………13

Figure2.7Basicwatermarkembeddingscheme……………………………………….14

Figure2.8BasicwatermarkingDecodingsystem………………………………………15

Figure2.9Classificationofwatermarkingalgorithmsbasedondomainusedforthe

watermarkingembeddingprocess……………………………………………………….16

Figure2.10Classificationofwatermarkingbasedonapplications…………………….17

Figure2.11Digitalwatermarkingrequirementstriangle………………………………20

Figure3.1WatermarksinMarkandDollarbanknotes………………………………...24

Figure3.2Visiblewatermark…………………………………………………………..24

Figure3.3Invisiblewatermark…………………………………………………………25

Figure3.4DeliveringDigitaldatatoatrustedEndsystem……………………...........26

Figure3.5DeliveringDigitaldatatothecustomer……………………………………26

Figure3.6Conflict:

AliceandBobcanbothdetecttheirrespectivewatermarkinimage

I…………………………………………………………………………………………28

Figure3.7ImageLenaCopyingordistributinginprintorelectronicformswithout

writtenpermission………………………………………………………………………31

Figure3.8TheembeddingschemeofthewatermarkingalgorithmasproposedbyCoxet

al.Alotoftheproposedwatermarkingtechniquessharethesamemodel……………..36

Figure3.9Thewaveletpyramidofthree-levelimagedecomposition.Eachlevelconsists

ofthreedetailimages,whichcorrespondtohorizontal,vertical,anddiagonaldetailsof

eachresolutionlevel.xystandsforapplyingfilterxinrowdirectionandfilteryincolumn

direction,whereLmeanslow-passfiltering,Hhigh-passfiltering,andCisthecoarse

image…………………………………………………………………………………….38

4

Figure4.1DWTthreeleveldecompositionflowchatofacolorimage………………...40

Figure4.2WatermarkEmbeddingAlgorithmflowchart………………………………42

Figure4.3WatermarkExtractionAlgorithmflowchart……………………………….44

Figure4.4InvisibilityExperiment（a）OriginalImage（b）WatermarkedImage………...45

Figure4.5WatermarkedImageSufferingvariouskindsofattacks（a,b,c,d）.....45

5

ListofTable

Table2.1Numberofpublicationsondigitalwatermarkingduringthepastfewyears

accordingtoWatermarkingworld.org………………………………………………..15

Table2.2Numberofpublicationsondigitalwatermarkingduringthepastfewyears

accordingtoINSPEC,Jan,1999.……………………………………………………….15

Table4.1TheDetectionresponsebetweentheextractedwatermarksandtheattacked

watermarkedimageunderdifferenttypesofattacks……………………………………46

IV

HunanUniversity

StatementofOriginality

Iherebycertifythatthethesissubmittedisbasedontheresearchcarriedoutbymyself

independentlyundertheguidanceandsupervisionofmysupervisor.Anyideasor

quotationsfromtheworkofotherindividualandcollectiveworksarefullyacknowledged

inaccordancewiththestandardreferencingpracticesofthediscipline.

Author'sSignature:

Date:

-May,28,2007

CopyrightStatement

PermissionisherewithgrantedtoHunanUniversitytocirculateandtohavecopiedfor

non-commercialpurposes,atitsdiscretion,thisthesisupontherequestofindividualsor

institutions.Theauthordoesnotreserveotherpublicationrightsandthethesisnormay

extensiveextractsfromitbeprintedorotherwisereproducedwithouttheauthor'swritten

permission.

Thisthesisbelongsto:

1.Secure,andthispowerofattorneyisvalidafter____________.

2.NotSecure

（Pleasemarktheabovecorrespondingcheckbox）

Author'sSignature:

Date:

May,___,2007

Supervisor'sSignature:

Date:

May,___,2007

1

Chapter1Introduction

1.1Preamble

Inrecentyears,thedevelopmentoftheInternetandmultimediatechnology,itiseasierto

produce,distribute,acquireandcopydigitalmediaproductssuchasdigitaltext,image,

videoandaudio[1].Thatiswhy,itisnecessarytoprotectthedigitalproduction.The

digitalwatermarkingtechniquecansolvetheproblem.Thedigitalwatermarkwhichis

representstheownershipoftheowneraccordingtotheembeddinginformationintothe

originalimage.Itcanbeappliedtodifferentapplicationsincludingdigitalsignatures,

fingerprinting,broadcastandpublicationmonitoring,authentication,copycontroland

secretcommunication[2].Usually,aneffectivedigitalwatermarkschemeprovidesthe

threemajorproperties[3].（i）Imperceptibility（ii）Robustnessand（iii）Unambiguity.The

embeddedwatermarkingmustbeimperceptibilityandinvisiblebecauseoftwoprimary

concerns;firstlyweshouldnotlowerthequalityoftheoriginalimageoritwillthebreak

theaestheticfeelinganddiminishthecommercialvalueoftheoriginal.Second,ifthe

watermarkembeddedisdetectedbyhacker,itwillbeeasilybrokeorberemoved.

Watermarkedimageshouldberobust.Thewatermarkcouldstillbeextractedclearlyafter

somedigitalimageprocessingsuchaslossyorlosslessimagecompression.Inthe

watermarkextractionprocess,itshouldbeunambiguoustoprovetheownershipofthe

owner[3].Oneoftheprimarywatermarkingdesigningconsiderationsisthatthe

invisibilityandrobustnessoftencollide[4].Inordertoimprovetherobustnessofthe

watermarkingscheme,wemustembedmoreandmorewatermarkinformationand

thereforecausethequalityoftheimagelowerandlower.Itseemslikethattheoriginal

imagehasbeeninterferedwithmuchmorenoise.Ontheotherhand,inordertokeepthe

qualityoftheoriginalimage,weembedfewerinformationandhighrobustof

watermarkingscheme.Usually,therearetwokindsofbasicwatermarkingdesignscheme

[4][5],

（1）Spatialdomainand

（2）TransformdomainorFrequencydomain（DCT,DWT,

DFT）.Thewatermarkismorerobustinthefrequencydomainthaninthespatialdomain.

Sothemethodwechoosefrequencydomaintoembedthewatermark.Therearemany

2

researchesanddevelopshavebeendonegrayscaleimagebutthecolorimageisnot

sufficient.Nowadaycolorimageisdominantmostofthepartsofapplications.

EmbeddinginformationincolorimageRGBcolorchannelishighlycorrelatedsoitisnot

suitableforembeddingwatermark.Someproposedembeddingschemesfocuson

embeddingwatermarksintheYcomponent（luminance）inYIQmodel.Kutteretal[6]

embedthewatermarkbymodifyingselectedsetpixelsinthebluechannelbecauseofits

lowsensitivitytohumanperception.ThebluechannelisthebestchoosetoJPEG

compressionamongtheRGBbecauseofitslowsensitivitytohumanperception.Sothe

hiddenwatermarkiseasytobelost.RedChannelembeddingwatermarkproblemisits

verylargeenergyloss.DuringtheRGBtruecolorimagecompressedintoJEPG,the

embeddingwatermarkintheredchanneliseasytolostanddifficulttoextract.Otherwise

greenchannelcanendureJEPGcompressionandtheembeddedwatermarkisrobust

enough.SoourselectisGreenchanneltoembedwatermarkinformationtoexamineit’s

capability.

1.2Motivation

Modernageistheageofdigitaltechnologies.Thedigitalinformationexchangelikeas

Internetandmultimediatechnologybecomeseasiertoproduce,distribute,modify,

acquireandcopydigitalmediaproductssuchasdigitaltext,image,videoandaudio.But

theseresultscreateseriousproblembecauseunauthorizedcopyingandmodificationof

thecontext.Anyonecaneasilycopythedigitalproductsfrominternetanditbecomes

veryeasytogetbenefitfromitwithoutownerpermission.Eventheycanclaimthatthey

aretheownersofthecopyright.

Forthisreasonpiracybecomesgreatthreatforinnovationandbusiness.Inordertosolve

intellectualpropertyproblemsofthedigitalage,theownerhavetheprotecti