文献翻译——多通道音频信息隐藏

第0页外文文献资料MULTI-CHANNELAUDIOINFORMATIONHIDINGABSTRACTWeconsideramethodofhidingmanyaudiochannelsinonehostsignal.Thepurposeofthisistoprovideamixthatincorporatesinformationonallthechannelsusedtoproduceit,therebyallowingall,or,atleastsomechannelstobestoredinthemixforlateruse.Afterprovidinganoverviewofsomerecentlypublishedaudiowatermarkingschemesinthetimeandtransformdomains,wepresentamethodthatisbasedonusingafourleastsignicantbitsschemetoembedveMP3lesintoasingle16-bithoststereoWAVlewithoutincurringanyperceptualaudiodistortionsinthehostdata.ThehostWAVleistakentobethenalmixassociatedwiththeoriginaldatabeforeapplyingloseMP3compressionoralternativelyanarbitraryhostaudiosignalintowhichothermultichannelaudiodataishidden.Further,theembeddedinformationcanbeencryptedand/ortheembeddinglocationsrandomizedonachannelbychannelbasisdependingontheprotocoldesiredbytheuser.Themethodisillustratedbyprovidingexamplem-codeforinterestedreaderstoinvestigateandreproducetheresultsobtainedtodateandasabasisforfurtherdevelopment.1.INTRODUCTIONTheapproachtoinformationhidingdiscussedinthispaperrelatestoaninvestigationintothedesignofintelligentcodingalgorithmsforaudiopost-productionbasedonacurrentFP7researchproject.TheresearchhasandiscontinuingtobeundertakenjointlybetweentheAudioResearchGroup,theDigitalMediaCentreatDublinInstituteofTechnologyandTamborineProductionsLimited.Thisincludestheuseofwatermarkingmethodsforaudiosignalauthenticationandmultipleaudio第1页signalembeddingtechniquesusingcomputationalsolutionsbasedonimageinformationhidingandauthenticationtechniques,e.g.Whilethereareanumberofdifferentapproachesforhidingasignalinanotherhostsignal,inclusiveofencryption,orotherwise,therearerelativelyfewpublishedmethodsthatconsideramulti-signaltosinglehostsignalapproach.InthispaperweconsidertheproblemofembeddingmanyaudiosignalsprovideasinMP3formatsintoasinglewaveofWAVleunderthefollowingconditions:(i)theembeddedMP3audiodatacanberecoveredwithoutanylossofinformation;(ii)thehostsignalhasnoperceptualchangeinitsaudiodelity.AnalgorithmispresentedbasedonatimedomainmethodinwhichveMP3lesarehiddeninasingleWAVleusingafourleastsignicantbitschemewhichsatisestheseconditions.Themethodconsideredhasapplicationsincovertinformationtransmissionwithapplicationsinareassuchascommunicationssecurity,signalauthenticationandDRM(DigitalRightsManagement),forexample.However,themethodreportedhasbeendevelopedinthecontextofanaudiopost-productionproducttoallowsastereomixtoincorporateinformationonallorsomeofthechannelsusedtoproducethesamemix,therebyallowingallorselectivechannelstobeembeddedinthemixforremixingatalaterdateand/orfordatastorage.Currentscenariosusuallyinvolvesapost-productioncentrehavingtomaintainrecordsofallthedatausedtogenerateamixwiththeviewthatthissamedatamayberequiredatalaterdate,therebynecessitatingtheneedforadatabasemanagementinfrastructurewhichmayrequiresignicantoverheads.Afterprovidinganoverviewofrecentlypublishedworksthatfocusontheareaofaudioinformationhiding(Section2),wepresentatimedomainsolutiontotheprobleminSection3.Thisincludesprototypem-codeforinterestedreaderstotestthealgorithmsforthemselvesandasabasisfordevelopingthemethodologyfurther.第2页2.AUDIOINFORMATIONHIDINGAudioinformationhidingorAudioSteganographyisbasedontwospecicanddistinctapproacheswhichconsiderthedevelopmentofalgorithmsusingtimedomaindataortransformdomaindatasuchastheconsinetransform,forexample.Inthissection,weprovideabriefoverviewofsomeofthemostrecentlypublishedmaterialinthisarea,publicationsthathavebeenstudiedbytheauthorsinassociationwiththemulti-channelinformationhidingapproachconsideredinthispaper.2.1.AudioHidingintheTimeDomainTimedomainaudiohidinghastheadvantageofbeingrelativesimpletoimplementandcomputationallyefcient.Howevertheapproachdoesnotyieldalgorithmsthatareasdiverseandrobustasthosedevelopedforthetransformdomain.Thisisbecauseoftherelativelylimitednumberofwaysinwhichdatacanbemanipulatedinthetimedomainsubjecttothegenerationofanoutputthatisperceptuallycompatiblewiththeoriginalaudiosignal.Intheliteraturesurveythatfollows,itisclearthatallthemethodsconceivedarebasedonsomeformofdatamanipulationbymodifyingthebinaryrepresentationoftheaudiosignal,i.e.variationsonthebasicthemeofmodifyingtheLeastSignicantBitsofadatastream.Forexample,in1,theauthorsproposedanovelaudioembeddingmethodusingamplitudedifferencing.Itinvolvesembeddingacovertmessageofanyformatintoatwocoveraudioleswhichareofasimilarsize.Thedifferenceinamplitudevaluesbetweenthetwosignalsiscomparedtothemaximumrangeindexoftherange(rangingfrom0to255whereallaudiovaluesarerepresentedasbytes).Thecovertmessageisdividedintoaseriesof4-bitsandnewamplitudedifferencevaluescalculatedforthetwocoveraudioleswhichcontainthemessage.Thisprocesshides2-bitsperaudiolewithatotalcapacityof4-bitsinbothles.Thedataextractionprocessfollowsthesameembeddingprocedure(intheinversesense).Themainadvantageofusingtwocoveraudiolesistodistributethepayloadequallyamong第3页morethanonelewhichpreventstheintroductionofnoiseintothecoverles.In2theauthorsproposetwonovelapproachesofLeastSignicantBit(LSB)substitutiontoimprovethecapacityoftheaudiohidingmethods.Therstapproachincreasesthenumberofbitsthatcanbeusedforhidingfrom4LSBsto7LSBsbyusingtherstandsecondMostSignicantBits(MSB),respectively,asfollow:(i)iftheMSB-1andMSB-2valuesare00then4LSBsareusedfordataembedding;(ii)ifthevaluesare01then5LSBsareused;(iii)ifthevaluesare10then6LSBsareused;(iv)ifthevaluesare11then7LSBsareusedfordataembedding.ThesecondapproachshiftsthemaximumlimitbyonlyconsideringtherstMSBwhere6LSBsareusedfordatahidingifitsvalueis0and7LSBsareusedifitsvalueis1.Thedataextractionprocedureusesthesamescenarioforretrievingtheembeddeddata(inaninversesense).Anencryptedwatermarkingschemeisdiscussed.Thesecretemessage(watermark)isencryptedusingabitexchangeencryptionmethodandtheencrypteddataembeddedintotheLSBandLSB+3bitsofthecoverle.Theembeddingprocessstartsbydividingeachbyteofthesecretmessageintogroupsoftwobits,therst2-bitsareembeddedintotheLSBandLSB+3bitsofthecoverleleavingonebyteintact.2-bitsarethenagainembeddedintotheLSBandLSB+3leavingonebyteintact.Thesameprocessisrepeatedforallbitsofthesecretmessagebitsyieldinganalgorithmthatembedsonebyteofthesecretmessageinto8bytesofthecoverle.In3theauthorspresenttwomethodstoimprovetheconventionalLSBmodicationmethodforaudiosteganography.TherstmethodisbasedonrandomizingtheLSBbitnumberofthehostle,thebitselectionbeingbasedonthe1stand2ndMSBs,respectively.IftheMSB-1andMSB-2valuesare00thenthe3rdLSBisusedforembeddingasecretbit;ifthevaluesare01thenthe2ndLSBisused,andifthevalues第4页are10or11thenthe1stLSBisused.Thesecondapproachrandomizesthesamplenumberscontainingthenextsecretbitofthedata,thedecisioncriterionrelyingontherst,secondandthirdMSBs:IftheMSB1,MSB2andMSB3valuesare000thenthesamplecontainingnextsecretbitisi+1;iftheirvaluesare001thenthesamplecontainingthenextsecretbitisi+2;iftheirvaluesare010thenthesamplecontainingthenextsecretbitisi+3,andsoon.Inbothcases(i.e.themethodsconsidered)dataextractionisperformedbycomparingtheMSBsvaluestondtheLSBswiththehiddendata.Differentlow-bitcodingmethodsforaudiosteganographyareconsidered.Conventionallow-bitcodingmethodsembedthebitsofthewatermarkintotheLSBsofthecoveraudio.Thiscanbeimprovedbyusingavariablelow-bitcodingusingtwoapproaches.Therstapproachdenestwothreshold(T1andT2)basedonthestandardlevelaboutamid-rangeof128wherethesamplesaretakentobebyteswithamaximumvalue255.IftheaudioamplitudevalueisgreaterthanT2,twobitsareusedforembedding.IftheamplitudevalueisbetweenT1andT1,onebitisusedtoembed,noembeddingbeingundertakenifthewatermarkdatahasavaluelessthanT1.Thesecondapproachcalculatestheaverageamplitudedataofthesurroundingaudiosignaltoprovideathreshold.Iftheamplitudelevelisgreaterthantheaveragevalue,then2-bitsareembeddedinthehostsignal,else,noembeddingisundertaken,theamplitudelevelbeingconsideredtobetoolow.2.2.AudioHidingintheTransformDomainUsingthetransformdomainprovidesthepotentialtogenerateawiderclassofaudioinformationhidingmethodsthanareavailableusingtimedomaintechniques.However,anytransformdomaincomesattheexpenseofthecomputationalcostsinvolvedincomputingthetransformanditsinversewhichistypicallytheFouriertransformcomputedusingafastFourierTransform(FFT)butincludestransformssuchastheDiscreteWaveletTransformandtheDiscreteCosineTransform.Forexample,in第5页4,anaudiowatermarkingalgorithmisconsideredbasedonaRSVD(ReducedSingularValueDecomposition)oftheFFToftheaudiosignal.Themethodreliesonmanipulatingthecoefcientsofoneoftheresultingunitarymatricesforwatermarkembedding.TheaudiosignalissplitintoframesoflengthL,aFFTappliedtocomputethemagnitudespectrumineachframe,and,nally,thefrequencycomponentsofeachframeisorganizedintoRSVDinputmatrix(RSVDbeingappliedtoamatrixratherthanavector).AnaudiowatermarkingalgorithmbasedonFastFourierTransformandQuadraticmatrixisconsideredin5.Anon-singularquadraticformischosentoobtainacorrespondingquadraticmatrixQandthesecretdataisconvertedintoamatrixMwhichistakentobeequivalenttoQ.ThesematricesarethenmultipliedtogenerateanencrypteddatamatrixE.ThecoveraudiodataistransformedintothefrequencydomainusingaFFTandthesecretinformationEembeddedintothefrequencydomainofthecoversignal.RetrievalisperformedbyrecoveringthehiddendataEtoregeneratetheaudiocoverfrequencydomainanddecryptionperformedbymultiplyingEbytheinversematrixQ1torecovertheoriginalwatermark.Ablindaudiowatermarkingalgorithmusingthewavelettransformchaoticencryptionispresented.Chaoticencryptionisusedforencryptingthewatermarkdataandrandomizingits(hiding)location.Thewatermarkbitstreamisencryptedandtheoriginalaudiosignaldividedintonon-overlappedframes.RandomizationoftheorderoftheframesisundertakenusingchaoticsequenceandeachframeprocessedwithanLgradewavelettransform.Finally,theencryptedwatermarkbitsareembeddedintotheLgradedetailvaluebychoosingMcoefcientsfromthegreaterabsolutevaluesbetweenthedetailvalues.Applicationofthewavelettransformcoupledwithhigher-orderstatistics.Thetwodimensionalwatermarkdata(imageoraudiosamplesorganizedintoamatrix)isinitiallyscrambledusingtheArnoldtransform第6页andconvertedintoonedimensionalsequenceofzerosandones.Awaveletde-noisingalgorithmisappliedtothehostaudiodatatoremoveasmuchnoiseaspossibleandrecoveritsoriginalcharacteristics.Thede-noisedaudiosignalaredividedintosegments,eachsegmentAbeingfurthersub-dividedintotwopartsA1andA2oflengthL1andL2elementsrespectively.TheembeddingprocessstartsbyembeddingasynchronizationcodeintotheaveragevalueoftheaudiosamplesofA1asdescribedinSection4.4givenwhichisrequiredtosurvivede-synchronization.ThewatermarkisembeddedintoA2asfollows:sub-divideA2intoaudiosub-segmentsoflengthL2/(MxNsamples(whereL2isthelengthofA2andMNisthewatermarksize),performanH-levelDWToneachsubsegment,embedthewatermarkintotheDWTcoefcientsbasedonthehigher-orderstatisticscomputedusingtheHausdorffdistanceandnallyapplyaninverseDWTtoobtainthewatermarkedaudiosegment.Thesynchronizationcodeandwatermarkbitsareembeddedintoeachaudiosegmenttoincreasetherobustnessofthemethod.Thewatermarkdetectionisperformedbyde-noisingthewatermarkedaudiosignal,detectingthesynchronizationcodeandusethedetectedcodestolocatethewatermarkintoaudiosubsegmentsbasedonhigher-orderstatistics.AnapproachusingSVD-DCT(SingularValueDecompositionDiscreteCosineTransform)andsynchronizationcodes.Thehostaudiosignalispartitionedintotwoparts,therstforsynchronizationcodeinsertionandthesecondforwatermarkembedding.Alogisticchaoticsequencewithaninitialvalueintheinterval0;1isusedtogeneratethesynchronizationcode.Toembedthewatermark,thehostaudiosignalisorganizedintoa2DmatrixHwhichisthensegmentedintonon-overlappingblocksHj.An8x8blockbasedSVDisusedtogenerateU,SandVandtherstSVDcoefcientsarrangedtoformS(1;1)ofeveryblockintoanewmatrixDCwheremostsignalenergyisconcentratedinthelargestsingularvalues.ThematrixDCis第7页partitionedinto44sub-blocksandtheDCTappliedtoeachblocktogeneratetheSVD-DCTcoefcientblocks.Thewatermarkembeddingstartsbyselectingthecoefcientpairstobemodied(theselectionisbasedonapseudo-randomsequence)fromthepotentiallocationofeachSVD-DCTblock.Thefrequencymaskiscomputedtoweightthewatermarkamplitude(thefrequencymaskisusedtodeterminetheleveloftoleranceagainstdistortioncausedbyembeddingthewatermark),and,nally,thewatermarkisembeddingbymodifyingthemagnitudedifferenceoftheselectedpairs.3.MULTI-CHANNELINFORMATIONEMBEDDINGNoneoftheaudiowatermarkingmethodsdiscussedintheprevioussectionandotherrecentpublicationsstudiedbytheauthorsconsidertheproblemofembeddingmultiplechannelsintoasinglechannel.Multi-channelwatermarkinghasanumberofpotentialadvantagesoversinglechannelwatermarking.Themostobviousoftheseisthatanumberofentirelyindependentanduncorrelatedsourcesof(audio)informationcanbeembeddedintoasingleaudiohostsignaleitherasplaintextorciphertextdatastreams(dependinguponwhetherdataencryptionofthehiddeninformationisrequired).TheschemeisbasedonembeddingveMP3lesintoasingleWAVleusing4LSBcoding.ItfocusesontheuseofveMP3lesintermsoftheoptimumnumberofchannelsthatcanbeembeddedsubjecttothefollowingconditions:minimalperceptualdistortionofthehostWAVleaccordingtothePerceptualEvaluationofAudioQuality(PEAQITU-RrecommendationBS.1387)discussedin32;highintegrityonthedelityofallchannelsafterextractionfromthehostsignalbasedon4-bitLSBcoding.Theuseof4-bitLSBistheminimumrequiredtosatisfythesecondoftheseconditionsandispredicatedonexperimentalresultsassociatedwiththerstcondition(detailsofwhichliebeyondthescopeofthis第8页paper).Thisapproachfollowsonfromthemethodreportedin33whichusesaFrequencyModulationmethodcalledChirp-Coding,originallydesignedforthepurposeofself-authenticatingdigitalsignals34modiedtoembeduptofourinformationpackets.However,theinformationcapacityoftheseinformationpacketsislowcomparedtothemethodproposedinthispaperaswellasbeingcomputationallymoreintensive.However,unlikethetechniquereportedhere,themethodgivenin33isrobusttovariousattackssubjecttothecarrierfrequencyofthechirpwherealowfrequencysweepprovidesgreaterrobustnesswhencomparedtoahighfrequencysweep.Inthiscase,thewatermarksequenceisderivedfromsub-bandenergieswhichareuniqueandsignaldependent.Duetothedifferentprocessesassociatedwithinformationextraction,anadditionaladvantageofself-authenticationisachieved,therebymakingthismulti-levelwatermarkingschemesimultaneouslyrobustandfragile(toanattack).Bycomparison,themethodproposedinthispaperisnottakentoberobustandisextremelyfragile.Inotherwords,thewatermarkedWAVlecannotbesubjectedtoanyformoflossycompressionorotherprocesswhichinvolvesdatadegradationalthoughlosslessencryptionispossibleifrequired.Themethodreportedin33isdesignedforsignalauthenticationusinglimitedinformationembeddingandfocusesonissuesassociatedwithDigitalRightManagementandCopyrightProtection.Theapproachconsideredinthispaperfocusesonattemptingtopackmanyaudiochannelsintoasingleaudiosignalwithminimallossofinformationwhilesustainingaudiodelityofthehostsignal.ReferringtoFigure1,theinputaudiochannelsaretakentobeMP3leswhichmaybylooselycompressedWAVles.TheMP3datavectorsareconcatenatedtoformasinglevectorexpressedinbytes.Thisvectorissplitintotwocomponentvectorscomposedof4-bitentries.ThehostWAVleisdecomposedintotwocomponentvectorsrepresentingthe第9页leftandrightchannelsofthestereodatastream.AnadditionalstepcanthenbeconsideredwherebyeachchannelisrandomizedintermsoftheembeddinglocationsfortheinputdataasillustratedinFigure1.Afurthersecurityfeatureispossiblebyencryptingtheinputdatavectorbeforeembeddingisundertaken.Thisextrastepcanbeexecutedbyusingapseudo-randomorpseudo-chaoticcipherwhichiseitherconvertedtobinaryformoroutputinbinaryformbasedonthemethodsdiscussedin35,forexample.Theinformationhidingprocessisaccomplishedinthetimedomainbyembeddingthe2-partinputvectorintothe2-componenthostvectorusing4-bitLSBinbothcases.Thestereostego-audiosignalisthenconstructedbycombiningthetwocomponentoutputintoasingleWAVles.ThealgorithmforreconstructionoftheembeddeddataisillustratedinFigure2.Afterreadingthestereostego-audioWAVle,thedataissplitintotwochannelsand,asrequired,thekeysusedtoobtainthepositionoftheembeddeddatainthechannels.Reconstructionoftheembeddeddataisthenundertakenbyextractingthe4-bitLSBsandarrangingthedatatoregeneratetheoriginal(byte)vector.Thisvectoristhensplitintotheveoriginalchannelsanddecompressedasrequired,therebyrecoveringtheoriginalWAVles.Prototypem-codeforexecutingtheseprocessesisprovidedinAppendixAandAppendixBwhichprovidesolutionfortheembeddingandextractionofdata,respectively.Inthisexample,embeddingpositionrandomizationandencryptionoftheinputdataisnotincluded.ItisassumedthatusershaveaccesstoMP3compressionsoftware.4.SUMMARYMulti-channelinformationhidinghasarangeofapplicationsbutthemethodpresentedinthispaperisfocusedonproblemsassociatedwithaudiopost-production,inparticular,theproblemofembeddingtheaudiosignalsusedtoproducedastereomixinthatmix.Clearly,thecurrent第10页solutiononlyprovidesasolutionfora5:1embeddingscenarioandreliesontheinputWAVlesbeinglooselyMP3compressed.However,bydouble,tripleandquadruplesamplingthehostle,itispossibletoembed10,15and20channelsintothemixusingtheproposedapproach.Fromaninformationtheoreticpointofview,itisclearlynotpossibletoembedmanychannelsintoonechannelwithoutsomelossofinformationintermsofboththeembeddeddataandthehost.However,providedtheresultdoesnotleadtodistortionsthatareperceptibleonanaudiobasis,suchdistortionscanbemadeacceptable.5.REFERENCES1K.Shafi,A.Sankaranarayanan,G.PrashanthandA.Mohan,ANovelAudioSteganographySchemeusingAmplitudeDifferencing,TrendsinInformationSciencesandComputing(TISC),163-167,17-19Dec.2010.2H.B.Kekre,A.Athawale,B.S.RaoandU.Athawale,IncreasingtheCapacityoftheCoverAudioSignalbyUsingMultipleLSBsforInformationHiding,EmergingTrendsinEngineeringandTechnology(ICETET),196-201,19-21Nov.20103M.Asad,J.GilaniandA.Khalid,AnEnhancedLeastSignificantBitModificationTechniqueforAudioSteganography,InternationalConferenceonComputerNetworksandInformationTechnology(ICCNIT),143-147,11-13July2011.4J.Wang,R.HealyandJ.Timoney,ANovelAudioWatermarkingAlgorithmBasedonReducedSingularValueDecomposition,Sixth