An authorization model for a public key management service

Public key management has received considerable attention from both the research and commercial communities as a useful primitive for secure electronic commerce and secure communication. While the mechanics of certifying and revoking public keys and escrow

© ACM, 2001. This is the authors' version of the work. It is posted here by permission of ACM for your personal use.Not for redistribution. The definitive version is available at http://doc.guandang.net/10.1145/503339.503343.

AnAuthorizationModelforaPublicKey

ManagementService

PIERANGELASAMARATI

Universit`adiMilano

MICHAELK.REITER

CarnegieMellonUniversity

and

SUSHILJAJODIA

GeorgeMasonUniversity

Publickeymanagementhasreceivedconsiderableattentionfromboththeresearchandcommercial

communitiesasausefulprimitiveforsecureelectroniccommerceandsecurecommunication.While

themechanicsofcertifyingandrevokingpublickeysandescrowingandrecoveringprivatekeys

havebeenwidelyexplored,lessattentionhasbeenpaidtoaccesscontrolframeworksforregulating

accesstostoredkeysbydifferentparties.Inthisarticleweproposesuchaframeworkforakey

managementservicethatsupportspublickeyregistration,lookup,andrevocation,andprivatekey

escrow,protecteduse(e.g.,todecryptselectedmessages),andrecovery.Weproposeanaccesscontrol

modelusingapolicybasedonprincipal,ownership,andauthorityrelationshipsonkeys.Themodel

allowsownerstogranttoothers(andrevoke)privilegestoexecutevariousactionsontheirkeys.

Thesimpleauthorizationlanguageisveryexpressive,enablingthespeci cationofauthorizations

forcompositesubjectsthatcanbefullyspeci ed(ground)orpartiallyspeci ed,thusmakingthe

authorizationsapplicabletoallsubjectssatisfyingsomeconditions.Weillustratehowtheaccess

controlpolicyandtheauthorizationscaneasilybeexpressedthroughasimpleandrestricted,hence

ef cientlycomputable,formoflogiclanguage.

CategoriesandSubjectDescriptors:D.4.6[OperatingSystems]:SecurityandProtection—Access

Controls;H.2.7[DatabaseManagement]:DatabaseAdministration—Security,integrity,andpro-

tection;K.6.5[ManagementofComputingandInformationSystems]:SecurityandProtection

GeneralTerms:Security

AdditionalKeyWordsandPhrases:Accesscontrol,authorizationsspeci cationandenforcement,

publickeyinfrastructure

TheworkofPierangelaSamaratiwaspartiallysupportedbytheEuropeanCommunitywithinthe

Fifth(EC)FrameworkProgrammeundercontractIST-1999-11791–FASTERproject.

Authors’addresses:PierangelaSamarati,DipartimentodiTecnologiedell’Informazione,Universit`a

diMilano,ViaBramante,65,26013Crema(CR),Italy;email:samarati@dsi.unimi.it;MichaelK.

Reiter,CarnegieMellonUniversity,Pittsburgh,PA15213;email:reiter@cmu.edu;SushilJajodia,

CenterforSecureInformationSystems,GeorgeMasonUniversity,Fairfax,VA22030-4444;email:

jajodia@gmu.edu.

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ACMTransactionsonInformationandSystemSecurity,Vol.4,No.4,November2001,Pages453–482.

Public key management has received considerable attention from both the research and commercial communities as a useful primitive for secure electronic commerce and secure communication. While the mechanics of certifying and revoking public keys and escrow

454 P.Samaratietal.

1.INTRODUCTION

Themechanicsofpublickeymanagement—i.e.,thecreationanddistributionofpublickeycerti catesandrevocationlists,andthesecurebackup(escrow)ofprivatekeys—hasbeenexploredextensively(e.g.,seeACM[1996]).However,muchlessattentionhasbeenpaidtotheauthorizationmodelthatmustsur-roundthesemechanisms.At rstglance,theauthorizationmodelseemsquitesimple:apublickeyshouldbeaccessibletoanyone,andanescrowedprivatekeyshouldbeaccessibleonlytoitsowners,astheirnamesindicates.Thissimplemodelis,however,fartoounderdevelopedformanyrealisticsettings.

—Onepurposeinescrowingaprivatekey,relevantmainlyinbusinesssettings,istodelegatetheauthoritytousethatkeytotheescrowingservice.Forexample,uponleavingforvacation,anexecutivemightescrowherprivatekeyattheserviceandauthorizethatitbeusedtodecryptmessagesuponrequestbyatleasttwoofherdirectreports.Whenshereturnsfromhervacation,shecancheckthelogsattheservicetoseewhatherkeywasusedtodecrypt.

—Itmaybedesirablethatsome“public”keysnotbepublicatall,butavailabletoonlyaselectedfewforverifyingsignaturesonprivatemessages.Inthisway,ifamessageisaccidentallyleakedfromanorganization,outsidersmuststillobtainacerti edverifyingkeytoprovethatthemessageactuallyorigi-natedfromwithintheorganization.Hiding“public”keyscanalsobeusefulforpreventingoutsidersfromsendingencryptedemailtotargetswithintheorganization.Encryptedemailcould,forinstance,beusedtoslipavirus-ladendocumentbyvirus-detectionsoftwareattheorganization’s rewall.—Theownerofapublickeymayconferrevocationauthoritytoothers,sothatoneofthemcanrevokethepublickeyiftheprivatekeyisstolenandtheowner’scopyisdestroyed.

Accesscontrolforpublickeymanagementservicesmustalsoaddressthepeculiaritiesofdealingwithkeysasobjectsofauthorizations.Inparticular,keysenjoyamoredynamicbehaviorthantraditionalobjects/resources,whichraisestheissueofhowkeysshouldbereferredto(e.g.,viatheirvaluesortheirprincipals).Also, …… 此处隐藏：45211字，全部文档内容请下载后查看。喜欢就下载吧 ……