Multidimensional data encryption with digital holography.docx

Multidimensional data encryption with digital holography.docx

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Multidimensionaldataencryptionwithdigitalholography

Multidimensionaldataencryptionwithdigitalholography

LingfengYu

andLilongCai

DepartmentofMechanicalEngineering,HongKongUniversityofScienceandTechnology,ClearWaterBay,Kowloon,HongKong

Received10May2002; 

revised28September2002; 

accepted2December2002. ;

Availableonline11December2002.

Abstract

Anewmethodbasedontheconceptofvirtualopticsforbothencryptionanddecryptionisproposed.Itanalyzesthepotentialreasonsofthelimitationsofourearlierworkandpresentssomenewapproachtoimprovetheoriginalalgorithm.Differentmethodsofnumericalreconstructionfordataencryptionarecompared,thelimitationscausedbyoff-axissetupsarediscussed,andtheresolutionofthedecryptedimagecouldbeflexiblyadjusted,whichmakesitpossibletodecrypttheimagewithvirtuallynolossofdata.Numericalexperimentsareperformedtovalidatetheproposedmethod,andsensitivitiesofsomeparametersarequantitativelyanalyzedandillustrated.

AuthorKeywords:

Informationsecurity;Encryption/decryption;Digitalholography;Virtualoptics

ArticleOutline

1.Introduction

2.Differentmethodsfordigitalholography

3.Principlesofencryptionwithvirtualoptics

3.1.Recordingahologramoftheobject

3.2.ReconstructionoftheobjectwithSMM

3.3.Implementationofdataencryptionanddecryption

4.Numericalexperimentsandresults

4.1.ComparingSMMwiththeFTM

4.2.Effectofdifferentsizeofthe“virtualhologram”

4.3.Sensitivitiesofdifferentparameters

5.Conclusion

Acknowledgements

References

1.Introduction

Informationhidingtechniqueshaverecentlybecomeimportantinanumberofapplicationareas.Digitalaudio,video,andpicturesareincreasinglyfurnishedwithdistinguishingbutimperceptiblemarks,whichmaycontainahiddencopyrightnoticeorserialnumberstopreventunauthorizedcopying.Militarycommunicationsystemmakesincreasinguseoftrafficsecuritytechniques,whichseektoconcealitssender,itsreceiver,oritsveryexistence,ratherthanmerelyconcealthecontentofamessageusingencryption.Similartechniquesareusedinsomemobilephonesystems,intellectualpropertiesprotections,andschemesproposedforelectroniccommunications.

Criminalstrytousewhatevertrafficsecuritypropertiesthatareprovidedinternationallyorotherwiseintheavailablecommunicationsystems.Acompetitionisgoingonbetweenthedevelopersofdatasecuritysystemsandcounterfeiters.Theraceisescalatingasthetechnologyforperpetratinginformationfraudbecomesincreasinglycommon.Asadvancedhigh-speedcomputersbecomemoreandmoreavailable,thetimerequiredtodecipheranencodedmessageisrapidlyreduced,thusevenhighlysophisticatedencryptiontechniquescouldbecomeincreasinglyvulnerable.Thisserioussituationisapowerfuldrivingforceforunceasingdevelopmentofvariousidentityauthenticationanddataencryptiontechnologies[1].Otherclosetechnologiesrelevanttodataencryptionintermsofdataprotectionandidentifyauthenticationarewatermarking[2]andbiometrics[3].

Overpastfewyears,someresearchershavestartedexploringvariousopticalmethodsfordataencryption,becauseopticalinformationprocessingtechniqueshaveobviousadvantagessuchasinherentparallelprocessingcapability,moredegreesoffreedom（e.g.,amplitude,phase,polarization,wavelength）forencryptionanddecryption,andhigh-leveldatasecurity,incontrasttotheirelectroniccounterparts.Forinstance,twoindependentrandom-phasemaskshavebeenusedinaconventionalopticalprocessorforencryptinganimage[4].Inthisapproach,thefirstrandommaskwasbondedwithaninputimage,andanotherwasplacedintheFourierplaneoftheprocessorforencryptingtheinputimage.TherandomphasemasksintheFourierplanecanserveasasecuritykeyfordecryption.Sincetheinputimageispositive,itispossibletoreconstructtheencryptedimage,withtheproperkey,fromitsFouriermagnitude.So,anopticalFouriertransformandstatisticalaveragingprocesswasemployedtodecodetheencryptedimage.Inanotherapproach[5],acomputer-generatedhologram（CGH）techniquehasbeenusedforsecurityauthentication.Apoint-orientedCGHandacell-orientedCGHaresynthesizedbyelectronicbeamlithographytogeneratemultipleimageplanes.EachreconstructedimageisroughlythesameasthatofaCGHcontainingonlyasinglewavefrontofthecorrespondingobject.Anotherexampleusingopticalmethodsforencipheringdataisthemethodofencryptingtwo-dimensionaldatabasedonorthogonal-phase-codemultiplexing[6].Recently,a“three-dimensionalkey”technique[7],withtworandom-phasemasksplacedinaFresneldomain,hasalsobeenproposedtoincreasethesecurityofopticalencryption.Thephase-conjugatetechniqueisem