RFID Systems and Security and Privacy.docx

RFID Systems and Security and Privacy.docx

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RFIDSystemsandSecurityandPrivacy

RFIDSystemsandSecurityandPrivacy

Implications

Abstract.TheAuto-IDCenterisdevelopinglow-costradiofrequency

identification（RFID）basedsystemswiththeinitialapplicationasnext

generationbar-codes.WedescribeRFIDtechnology,summarizeourapproachandourresearch,andmostimportantly,describetheresearch

opportunitiesinRFIDforexpertsincryptographyandinformationsecurity.Thecommonthemeinlow-costRFIDsystemsisthatcomputation

resourcesareverylimited,andallaspectsoftheRFIDsystemareconnectedtoeachother.Understandingtheseconnectionsandtheresulting

designtrade-offsisanimportantprerequisitetoeffectivelyansweringthe

challengesofsecurityandprivacyinlow-costRFIDsystems.

AutomaticIdentification（Auto-ID）systemshavebecomecommonplaceinaccesscontrolandsecurityapplications,inindustriesrequiringthetrackingofproductsthroughthesupplychainormanufacturingprocess,andinindustriesrequiringtheidentificationofproductsatthepointofsaleorpointofservice.PerhapsthemostwidelyrecognizedAuto-IDsystemisthebarcodesystemdevelopedduringtheearly1970’s.Morerecently,Radio-FrequencyIdentification（RFID）systemshavebeguntofindgreateruseinautomaticidentificationapplications.RFIDsystemsconsistofRadioFrequency（RF）tags,ortransponders,andRFtagreaders,ortransceivers.Thetranspondersthemselvestypicallyconsistofintegratedcircuitsconnectedtoanantenna[8].Theuseofsilicon-basedmicrochipsenablesawiderangeoffunctionalitytobeintegratedintothetransponder.Typicalfunctionalityrangesfromlargeread/writememoriestointegratedtemperaturesensorstoencryp!

tionandaccesscontrolfunctionality.Thetransceiversquerythetranspondersforinformationstoredonthem.Thisinformationcanrangefromstaticidentificationnumberstouserwrittendatatosensorydata.

ThepotentialapplicationsforRFIDsystemsarenumerous.Consider,forexample,supplychainmanagementapplicationsandtheuseofEAN-UCCbarcodes.Today,over5billionbarcodesarescanneddailyworld-wide[6].Yet,mostbarcodesarescannedonlyonceduringthelifetimeoftheitem,namelyatthecheckout.RFIDsystems,ifstrategicallydeployed,areasingleplatformonwhichanumberofsupplychainmanagementapplicationscanbesimultaneouslyimplemented,benefitingallpartiesinvolvedinacommercialtransaction:

themanufacturers,theretailers,theusers,andevenregulatorybodies（suchastheFoodandDrugAdministration（RFDA）intheUnitedStates）.AutomateditemlevelinventoryidentificationusingRFIDsystemswillrevolutionizesupplychainmanagementbyenablingapplicationssuchasautomatedreal-timeinventorymonitoring（attheshelfandinthewarehouse）,automatedqualitycontrol,andautomaticcheck-out.

Thesignificantbenefitsthataninexpensive,openstandards-basedRFIDsystemcanprovidearewidelyunderstoodandacknowledged.Atthesametime,typicallow-costtranspondersarepricedintherangeofUS$0.50-US$1.00,andRFIDsystemslackwidelyacceptedandimplementedstandardsforcommunicationandfunctionality,therebylimitingtheirpracticalusefulnessandkeepingtheirsystemcoststoohighformanyapplications.Inordertoachievesignificantitem-levelpenetrationwithinmostsupplychainapplications,transponderswillneedtobepricedwellunderUS$0.10,andpreferablyunderUS$0.05.Thesecosttargetscannotbeachievedwithoutasystem-levelapproachthatencompasseseveryaspectoftheRFIDtechnology,fromICdesigntoRFprotocols,fromreaderdesigntoback-enddatasystems,andfromICmanufacturingtoantennamanufacturing.Thechallengehasbeentodevelopacompleteopenstandards-basedsystemthatenablesthedesignandmanufactureoflo!

w-costRFIDsystems.TheAuto-IDCenter,anindustrysponsoredresearchcenterwithlaboratoriesatMassachusettsInstituteofTechnology,USA,CambridgeUniversity,UK,andtheUniversityofAdelaide,AU,hasdesigned,developed,anddeployedwithinalarge-scalefieldtrialanopenstandards-basedsystemthatenablestheuniqueidentificationofandretrievalofinformationonubiquitouslytaggeditems.TheCenter,inconjunctionwithitssponsors,hasalsoundertakenprojectstodesignandmanufactureopenstandardlow-costRFIDtransceiversandtransponderscapableoflittlemorethancommunicatingauniqueidentifierstoredwithinthem.Low-costtranspondersenablethetagginganduniqueidentificationofvirtuallyallman-madeitems.

Thecommercialavailabilityoflow-cost,Auto-IDCenterstandards-basedRFIDsystemsbymid-2003haspoisedthesesystemstobeoneoftheearliestandperhapsmostexplosiveopportunitiesinubiquitouscomputing.Asthesesystemsleavetheindustrialapplicationsandenterourdailylives,privacyandsecurityrelatedissueswillplayanincreasinglyimportantroleintheiruseandubiquity.Thepuposeofthispaperistoexplainthetechnology,thechallenges,andtheopportunitiesubiquitousRFIDsystemspresenttothesecurityandprivacycommunities.

Typicaltransponders（transmitters/responders）consistofamicrochipthatstoresdataandacouplingelement,suchasacoiledantenna,usedtocommunicateviaradiofrequencycommunication.Transpondersmaybeeitheractiveorpassive.Activetranspondershaveanon-tagpowersupply（suchasabattery）andactivelysendanRFsignalforcommunicationwhilepassivetranspondersobtainalloftheirpowerfromtheinterrogationsignalofthetransceiverandeitherreflectorloadmodulatethetransceiver’ssignalforcommunication.Mosttransponders,bothpassiveandactive,communicateonlywhentheyareinterrogatedbyatransceiver.

Typicaltransceivers（transmitter/receivers）,orRFIDreaders,consistofaradiofrequencymodule,acontrolunit,andacouplingelementtointerrogateelectronictagsviaradiofrequencycommunication.Inaddition,manytransceiversarefittedwithaninterfacethatenablesthemtocommunicatetheirreceiveddatatoadataprocessingsubsystem,e.g.,adatabaserunningonapersonalcomputer.TheuseofradiofrequenciesforcommunicationwithtranspondersallowsRFIDreaderstoreadpassiveRFIDtagsatsmalltomediumdistancesandactiveRFIDtagsatsmalltolargedistancesevenwhenthetagsarelocatedinahostileenvironmentandareobscuredfromview.

ThebasiccomponentsofanRFIDsystemcombineinessentiallythesamemannerforallapplicationsandvariationsofRFIDsystems.Allobjectstobeidentifiedarephysicallytaggedwithtransponders.Thetypeoftagusedandthedatastoredonthetagvariesfromapplicationtoapplication.

Transceiversarestrategicallyplacedtointerrogatetagswheretheirdataisrequired.Forexample,anRFID-basedaccesscontrolsystemlocatesitsreadersattheentrypointstothesecurearea.Asportstimingsystem,meanwhile,locatesitsreadersatboththestartinglineandthefinishlineoftheevent.Thereaderscontinuouslyemitaninterrogationsignal.Theinterrogationsignalformsaninterrogationzonewithinwhichthetagsmayberead.Theactualsizeoftheinterrogationzoneisafunctionofthetransceiverandtranspondercharacteristics.Ingeneral,thegreatertheinterrogationsignalpowerandthehighertheinterrogationsignalfrequency,thelargertheinterrogationzone.Sendingpowertothetranspondersviathereader-to-tagcommunicationsignalisthebottleneckinachievinglargereadrangewithpassivetags.Activetagsdonotsufferfromthisdrawback;thus,theytypicallyhavelargercommunicationrangesthananotherwiseequivalentpassivetag.

Thetransceiversandtransponderssimplyprovidethemechanismforobtainingdata（andstoringdatainthecaseofwritabletags）associatedwithphysicalobjects.

PassiveRFIDsystemsarethemostpromisingtoprovidelow-costubiquitoustaggingcapabilitywithadequateperformanceformostsupplychainmanagementapplications.Theselow-costRFIDsystemsare,ofnecessity,veryresourcelimited,andtheextremecostpressuresmakethedesignofRFIDsystemsahighlycoupledproblemwithsensitivetrade-offs.Unlikeothercomputationsystemswhereitispossibletoabstractfunctionalityandthinkmodularly,almosteveryaspectofanRFIDsystemaffectseveryotheraspect.WepresentabriefoverviewofthecriticalcomponentsofRFIDtechnologyandsummarizesomeofthesetrade-offsinpassiveRFIDdesign.

PassiveRFIDtagsobtaintheiroperatingpowerbyharvestingenergyfromtheelectromagneticfieldofthereader’scommunicationsignal.Thelimitedresourcesofapassivetagrequireittobothharvestitsenergyandcommunicatewithareaderwithinanarrowfrequencybandaspermittedbyregulatoryagencies.Wedenotethecenterofthisfrequencybandbyf,andwerefertoRFIDsystemsoperatingatfrequencyfwiththeunderstandingthatthisisthecenterfrequencyofthebandwithinwhichitoperates.

Passivetagstypicallyobtaintheirpowerfromthecommunicationsignaleitherthroughinductivecouplingorfarfieldenergyharvesting.Inductivecouplingusesthemagneticfieldgeneratedbythecommunicationsignaltoinduceacurrentinitscouplingelement（usuallyacoiledantennaandacapacitor）.Thecurrentinducedinthecouplingelementchargestheon-tagcapacitorthatprovidestheoperatingvoltage,andpower,forthetag.Inthisway,inductivelycoupledsystemsbehavemuchlikelooselycoupledtransformers.Consequently,inductivecouplingworksonlyinthenear-fieldofthecommunicationsignal.Thenearfieldforafrequencyfextendsupto1/（2πf）metersfromthesignalsource.

Foragiventag,theoperatingvoltageobtainedatadistancedfromthereaderisdirectlyproportionaltothefluxdensityatthatdistance.Themagneticfield