Deterministic phase encoding encryption in single shot digit

光学加密技术,双随机相位编码加密技术,傅立叶变换加密技术,全息加密技术

ApplPhysB(2008)93:473–479DOI10.1007/s00340-008-3201-5

Deterministicphaseencodingencryptioninsingleshotdigitalholography

G.-L.Chen·W.-K.Yang·J.C.Wang·C.-C.Chang

Received:9September2007/Revisedversion:31July2008/Publishedonline:13September2008©Springer-Verlag2008

AbstractWedemonstrateadeterministicphase-encodedencryptionsystembasedonthedigitalholographyandadoptedalenticularlensarray(LLA)sheetasaphasemodu-lator.Intheproposedschemetheholographicpatternsofen-cryptedimagesarecaptureddigitallybyadigitalCCD.Thisworkalsoadoptanovel,simpleandeffectivetechniquethatisusedtosuppressnumericallythemajorblurringcausedbythezero-orderimageinthenumericalreconstruction.Thedecryptionkeyisacquiredasadigitalhologram,calledthekeyhologram.Therefore,theretrievaloftheoriginalinfor-mationcanbeachievedbymultiplyingtheencryptedholo-gramwithanumericalgeneratedphase-encodedwave.Thestorageandtransmissionofallhologramscanbecarriedoutbyall-digitalmeans.Simulationandexperimentalre-sultsdemonstratethattheproposedapproachcanbeoper-atedinsingleprocedureonlyandrepresentthesatisfactorydecryptedimage.Finally,rotatingandshiftingtheLLAisappliedtoinvestigatethetoleranceofdecryptiontodemon-stratethefeasibilityintheholographicencryption,aswellascanalsobeusedtoprovidethehighersecurity.PACS42.40.-i·42.30.Wb·42.40.Ht

1Introduction

Inrecentyears,manyinformationsecurityusingopticalschemeshavebeenproposed[1–7]andtheinterestinphase-encodedmultiplexinghasincreasedmarkedly.Meanwhile,aseriesofdifferentphase-encodedmultiplexingschemeshavebeenreportedtoinvestigatethefeasibility[8–10].Denzetal.[8]mademuchprogresstowardsimplementinganapproachforrealizingbothdigitalandanalogholographicdatastoragebyencodingamatrixofreferencebeamswithorthogonalphases.Sunetal.[11]proposedtheuseofaground-glassdiffusertoperformrandom-phaseencoding.Theyutilizedtheirproposedapproachtorecord100pagesofvolumehologramsinaLiNbO3crystalwith0.01%Fedoping,achievingameanSNRoften.Theresearchfullyes-tablishedthepotentialofrandom-phaseencodedmultiplex-ingforopticaldatastorage.Theauthors’group[12]utilizedacircularholographicdiffuser(CHD)tomodulatethephaseofthereferencebeamforrandom-phaseencodingstorage.TheapproachrevealsthatrotatingandshiftingtheCHDcausesittoactasarandom-phasemodulatorintherefer-encebeamandconstituteasimplebuteffectiveapproachforincreasingthecapacityofholographicmemory.

Theuseofaground-glassorholographicdiffusertogeneraterandomphasehasalreadyshownitspotentialforphase-encodedmultiplexingandhigh-densitymultiplestor-age,alsotheexactlysamerandomphasecanonlybegen-eratedthroughtheoriginalone.Althoughgroundglassandholographicglassdiffusersbecomeimportantandnecessarywhenusedasahighlysecurephasekey[13,14],itisex-tremelydif culttoreplicatethekeyexactlyforthedecryp-tionprocedure.Thatis,therandom-phaseencodingcanbeusedtohideinformationandenhancethesecurity.However,iftherandom-phasekeyislostorbrokenthestoreddatacannotberead[15,16].Tosolvethisproblem,thiswork

G.-L.Chen·W.-K.Yang

SchoolofDefenseScience,NationalDefenseUniversity,Tashi,Taoyuan33509,Taiwan,ROC

J.C.Wang

DepartmentofAppliedChemistry&MaterialScience,NationalDefenseUniversityTashi,Taoyuan33509,Taiwan,ROCC.-C.Chang( )

InstituteofElectrophysics,MingDaoUniversity,Peetow,Changhua52345,Taiwan,ROCe-mail:chichang@mdu.edu.tw

光学加密技术,双随机相位编码加密技术,傅立叶变换加密技术,全息加密技术

474proposesanovelphase-encodedholographicencryptionap-proach.Alenticularlensarray(LLA)sheetusedasakeyisadoptedtocontrolthephaseencodingbytheauthortopre-ventthelossofencrypteddataevenifthekeylostorbroken.Intheproposeddatastoragescheme,thedigitalencryptedpatternsarecapturedholographicallyusingadigitalCCDwhereaLLAsheetisadoptedforphase-encodedmultiplex-ing.

Digitalholography,digitalholographicrecordingandwave-frontnumericalreconstruction,offersanalternativemethodforholographicrecordingandnumericalreconstruc-tion.Techniquesbasedondigitalholographyinthe eldofinformationsecurityhaveimportantbene tsinthe eldofinformationsecuritysincetheyenabledigitalstorage,trans-mission,anddecryptionofencrypteddata.Inthedigitalholographicencryption,adoptingthephase-encodedtech-niquesandusingadigitalCCDcameratotheholographicschemeeffectivelyextendthesecrecytothehiddeninfor-mation.Also,itisimpossibletoverifytheencrypteddoc-umentswithoutknowingthedecryptionkeythathasbeenusedintheencryption.However,theblurringofzero-orderimagehastobeeliminatedtoimprovetheresultofnu-mericalreconstruction.Kreisetal.developedamethodofsingle-exposurein-linedigitalholography[17,18].Intheirapproach,theso-calleddcterm,whichmainlyrepresentsthecontributionofthereferencewavetothezero-order,issuppressedbythesubtractionoftheaverageintensityofthehologram.However,theapplicationrestrainfromthatonlypartialzero-orderimageissuppressediftheobjectwavein-tensityisnotuniform[9].

Inthispaper,wedescribeanovelencryptionapproachthatutilizesthedigitalholographicencryptionbyusingthedeterministicphaseencodingwithasingle-stepdigitalholo-graphictechnique.Onebene toftheproposedopticalen-cryptionmethodoverthedigitalholographictechniquesisthattheprocesscanbeachievedbyalldigitalmeansforse-curinginformation.Thesecondbene tisthattheopticalen-cryptionisnaturallyuncomplicatedtoencrypttheinforma-tionorperformthedecryptioninsinglesteponly.Thethirdbene tisthatthephaseencodingcanbecontrolledbytheuser,aswellaspreventingthelossofdatawhichhasbeenencryptedinthedigitalhologrameventhoughthekeyhasbeenlostorbroken.

2Operatingprinciples

Inholographicphase-encodedencryption,aphasemodula-torencodesasecondwave,mutuallycoherentwiththe rst

(amplitudeandphase)asareferencewavethatisappliedtointerfereorencrypttheotherwavewhichisusedastheob-jectwave,denotedasψO.Meanwhile,thereferencewaveisformedfromaplanewavemodulatedbythedeterminis-ticphaseencoding,thusthemodulatedreferencewavecan

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