基于蛇行扫描序列的隐写技术(IJIGSP-V5-N6-4)

I.J.Image,GraphicsandSignalProcessing,2013,6,25-32PublishedOnlineMay2013inMECS()DOI:10.5815/ijigsp.2013.06.04Copyright©2013MECSI.J.Image,GraphicsandSignalProcessing,2013,6,25-32ANewSteganographyTechniqueUsingSnakeScanOrderingStrategyRajeevKumar,KhushilK.Saini,andSatishChandDivisionofComputerEngineering,NetajiSubhasInstituteofTechnology,Delhi,[e-mail],[e-mail],[e-mail]—Inthispaper,weproposeanewsteganographytechniqueusingthesnakescanorderingstrategy.Theproposedmethodhidesthesecretdatathatisanimageinanotherimage,knownasthecoverimage.Inthismethod,thepixelvaluesofthesecretimageareorganizedinsnakescanorder,whicharepreprocessedtoreducetheirsize.TheresultantdataisembeddedintotheLeastSignificantBits(LSBs)ofthepixelsofthecoverimage.Tominimizetheerror/distortion,thepixelvaluesofthestegoimageareadjustedusingOptimalPixelAdjustmentProcess(OPAP).TheperformanceoftheproposedmethodiscomparedwiththatofthesimpleLSBsubstitutionmethod,Changetal.method,Thein&Linmethod,andChenmethodintermsofPeakSignaltoNoiseRatio(PSNR).OurproposedmethodhashigherPSNRinalmostallcases.IndexTerms—Steganography,coverimage,stegoimage,snakescanorderingstrategy,PSNRI.INTRODUCTIONDuetoadvancementsincomputingandcommunicationtechnologies,acommunicationcanbeestablishedbetweentwoormorepersonsbeingatdifferentplacesthroughthecomputernetworksorusingInternetincasetheyareatdistance,whichrequireslargeresourcesintermsofmoneyandtimetomovephysicallytothedestination.Somemessages,whicharesupposedtobeveryimportantandtheirrevelationmaycauseunrepairabledamage,cannotbetransmittedintheiroriginalform.Thesetypesofmessagesareknownasconfidentialmessageandtheymustbecommunicatedinaverysecureway.Oneofthepossiblewaysistoencryptthemessagebeforesendingit.Thetransmissionofsecretmessagemayalsobeusedauthenticatingthemediaitself.Oneoftheimportantmediatotransmitasecretmessageisimagedata.Thesecrettobetransmittediscalledthesecretdataandtheimagedataiscalledthecoverimage.Iftheexistenceoftheconfidentialdatainthecoverimageisdetectedbyamasquerader,itcanbemisusedfordifferentpurposes.Suchencryptionprocessissaidtobevulnerable.Thesolutiontothistypeofproblemcanbesteganography.Thesteganographyistheartofconcealingsecretdataintoacarrierforconveyingthesecretmessageconfidentially[1],[2].Thebasicmodelofsteganographyusesthecovermediainwhichthesecretdataisembedded,thesecretdatathatistobehidden,andthealgorithmwithsecretkeythroughwhichthesecretdataisembeddedintothecovermedia.Theoutcomeofthisprocessisstegomedia(themediathathasthesecretmessage)thatissenttothereceiver.Theword‗steganography‘isthecombinationoftwoGreekwords-steganoandgraphy,whichmeancoveredandwriting,respectively,inEnglish.Ithasbeenusedpracticallysinceancienttime.Thesteganographyhasmanyapplicationsintoday‘slifesuchasdigitalwatermarkingforauthenticationpurpose,ortomaintainconfidentialityaswellasintegrityofthevaluabledatainordertoavoidaccessbyanunauthorizeduserormasquerader.Inimagesteganography,thecovermediaisthecoverimageandthestegomediaisthestegoimage.Theimagesinacomputersystemarestoredasanarrayofpixels,whichcanbegrayorcoloredimages.Thegrayscaleimages,alsocalledintensityimages,haveonlyonchannelandeachpixelisgenerallyrepresentedintermsof8bits.Incoloredimages,thearrayisacombinationofthreecolors:red(R),green(G)andblue(B).Thesearealsocalledchannels.Thenumericvalue(whichisintherangeof0-255fordigitalimagesrepresentedbyusing8bitsperpixel)ofeachpixeliscalledtheintensityofthatpixel.Forrepresentingacolorcomponentby8bitsrequires24bitsperpixel.Thepixelsinadigitalimagearewidelyusedtohidethesecretdataontheinternet.Theimagescanbemanipulatedineitherspatialdomainorfrequencydomainandaccordinglytherearetwomainclassesintowhichthesteganographytechniquesmaybedivided.TransformbasedtechniquesSpatialdomainbasedtechniquesThetransformbasedtechniques[3,4]havebeeninspiredbythefunctioningoftheHumanVisualSystem(HVS).Thehumaneyesaremoresensitivetorandomnoiseinsmoothareathaninthebusyarea.Thus,moredatacanbehiddeninbusyregionsthanthesmootherregionsbecausethedegradationoftheimagequalityismorenoticeableinsmootherregions.Inatransformbasedtechnique,thecoverimageistransformedintofrequencydomainbyapplyingaunitarytransformtotheoriginalimage.Theunitarytransformbreakstheoriginalimageintodifferentfrequenciesanditsinversetransform(matrix)issimplytransposeoftheoriginaltransformation(matrix).Theunitarytransformsinclude26ANewSteganographyTechniqueUsingSnakeScanOrderingStrategyCopyright©2013MECSI.J.Image,GraphicsandSignalProcessing,2013,6,25-32asDiscreteFourierTransform(DFT),DiscreteCosineTransform(DCT)orDiscreteWaveletTransform(DWT).Thesecretdataisthenembeddedintothehighfrequencycoefficients[5].Thesetypesofmethodsaremoresecureandrobust;theyarehowevermorecomplexandslowerthanthespatialdomainbasedmethodsasweneedtoapplytransformandinversetransformoperation.Thespatialdomainbasedtechniques[6,7]hidethesecretmessagedirectlyintothepixelintensityofthecoverimage.Inoneoftheimportanttypeoftechniques,someprespecifiedbitsofth