VerifiableAB-PREforSecurePublicCloudDataSharingContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREInstantiationsSecurityanalysisAdvantagesofourAB-VPREschemesConclusions02ContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREInstantiationsSecurityanalysisAdvantagesofourAB-VPREschemesConclusions03DataStoragePrivacyIntactnessApplicabilityAccessControlLargeServersThinClients

Achievingdataprivacyandfine-grainedaccesscontrol.Applyingtothinclients.Updatingtheaccesscontrol.Tosolvethefollowingissues:Introduction04ContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREInstantiationsSecurityanalysisAdvantagesofourAB-VPREschemesConclusions05ORANDBobUnionHospitalChiefPhysiciansEncryption:Specifythequalifiedusersbyanaccesspolicyorasetofattributes.Keygeneration:Associatedwithusers’attributecharacteristic.Decryption:Accomplishedonlyifattributesandtheaccesspolicyarematched.UserAUserB

UnionHospitalChiefPhysician

BobAttribute-basedEncryption(ABE)06ORANDBobUnionHospitalUserAUserB

BobAttribute-basedEncryption(ABE)

UnionHospitalChiefPhysician

Bobisinanemergency.AlltheChiefPhysiciansareunavailable.Scenario:ChiefPhysiciansHowtoderiveBob’smedicalrecords?MedicalRecords07ProxyRe-encryption(PRE)UserAUserBProxy

Theproxycannotseetheplaintext.TheproxycannotderivethesecretkeyofUserA.SecurityRequirements:08Attribute-basedPRE(AB-PRE)

Updatingaccesscontrolfromdelegation.Theproxycannotderivetheplaintextandtheprivatekey.AB-PREisdividedintoCP-AB-PREandKP-AB-PRE.09Attribute-basedPRE(AB-PRE)

Liangetal.(ASIACCS’09):ThefirstCP-AB-PRE.Luoetal.(ICICS’10):CP-AB-PREwithmulti-valuepositiveattributes.Yuetal.(INFOCOM’10):KP-AB-PREforuserrevocation.Yuetal.(ASIACCS’10):CP-ABE-PREforattributerevocationbutnotcollusionresistant.Liangetal.(FGCS2014):CCAsecureCP-AB-PREbasedonLSSS.Liangetal.(TIFS2015):CCAsecuresearchableKP-AB-PREintherandomoraclemodel.Assumingtheproxyissemi-trusted!10ContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREInstantiationsSecurityanalysisAdvantagesofourAB-VPREschemesConclusions11Non-interactiveVerifiableComputation

Gennaroetal.(Crypto’10):VerifyingarbitrarydelegatingcomputationbasedonaFHEscheme.Chungetal.(Crypto’10):ImprovedGennaroetal’sscheme.Parnoetal.(TCC’12):PublicdelegationandpublicverifiabilityfromABEschemes.Goldwasseretal.(Eprint’12):Publicverifiableandsecretdelegatingcomputationforgeneralfunctions.Notsufficientlyefficientandimpractical!12VerifiableOutsourcedComputationforABEGreenetal.(USENIX’11):OutsourcingthedecryptionofABEbykeyblindingtechnique.Laietal.(TIFS2013):VerifiableoutsourceddecryptionforABEwhichdoublesthecomputationandcommunicationcostscomparedtotheunderlyingABEscheme.Linetal.(TIFS2015):GenericconstructionofVO-ABEwheretheinstantiationimprovedtheefficiencyofLaietal.’sscheme.13Disadvantage:Exposureofthekeyblindingfactordirectlyrevealstheprivatekey.ApplyingtoAB-PRE?ContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREInstantiationsSecurityanalysisAdvantagesofourAB-VPREschemesConclusions14VerifiableAttribute-basedPRE(AB-VPRE)

Updatingaccesscontrolfromdelegation.Theproxycannotderivetheplaintextandtheprivatekey.AB-PREisdividedintoCP-AB-PREandKP-AB-PRE.Verification15ContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREInstantiationsSecurityanalysisAdvantagesofourAB-VPREschemesConclusions16OurTechniques

CombiningacommitmentschemeandaKDFduringtheencryption.Verificationincludestwosteps:(1)Invarianttest;(2)Correctdetection.Ourtechniques:Theproxyisuntrusted!Verification17ContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREOutlineofourconstructionAlgorithmdescriptions1819AB-KEMSKE+CommitmentKDFKEMDEM+VerifiabilityOutlineofOurConstructionSKRKAB-PREABEKeyblindingmultiplierNewaccesspolicy/attributessetABE20AB-KEMSKE+CommitmentKDFKEMDEM+VerifiabilitySKRKABEKeyblindingmultiplierNewaccesspolicy/attributesetCTRKCT’ProxyAB-PREABEOutlineofOurConstruction21CTRKCSSRCS(proxy)CTCT’CT’Ver:1Ver:2Ver:1CheckingfortheinvariantcomponentsofCT.Ver:2ExaminingthecalculationcorrectnessofCT’.AB-VPREOutlineofOurConstruction22AB-KEMSKE+CommitmentKDFKEMDEM+VerifiabilityEncryptionProxyRe-encryptionDecryptionKeyblindingAccesscontrolUpdateVerificationOutlineofOurConstructionContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREOutlineofourconstructionAlgorithmdescriptions2324AB-KEMSKE+CommitmentKDFKEMDEM+VerifiabilityEncSK=(K,L)RK=(K,L’,Enc’(D,I’_enc))RKGenABEKeyblindingmultiplierDNewaccesspolicy/attributesetREncCT_{I_enc}CT_{I’_enc}RKAlgorithmDescriptions25Ver2+RDecCT_{I_enc},CT_{I’_enc}b=0orb=1?Ver:1⊥b=0RDec(SK’,CT_{I’_enc},b)b=1Pass?⊥NoVer:2MYesVer1AlgorithmDescriptionsContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPRESecurityanalysis

Dataprivacyandverificationsoundness.

WeakMasterkeysecurity.2627SemanticallysecureComputationalhiding+bindingIND-CPAKDFsecureIND-CPA+VerificationSoundnessSecurityAnalysisforAB-VPREAB-KEMSKECommitment

Dataprivacyandverificationsoundness.AB-VPRE28SecurityAnalysisforAB-VPRE

WeakMasterkeysecurity.SelectivelyWeakMasterKeySecuritySelectivelyIND-CPACDHAssumptionAB-VPRENote:ExposureofthekeyblindingmultiplierprovidesnohelpforrevealingtheprivatekeyduetotheCDHAssumption.ContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREInstantiationsSecurityanalysisAdvantagesofourAB-VPREschemesConclusions2930AB-KEMOne-timepad+PedersenCommitmentKDFKEMDEM+VerifiabilityInstantiationsofAB-VPRESchemesAB-KEMAccesspolicyAB-VPRE-1CP(Liang’09)Non-monotonicAB-VPRE-2CP(Waters’11)LSSSAB-VPRE-3KP(Goyal’06)LSSSContentsIntroductionVerifiableattribute-basedPRE(AB-VPRE)ABE,PRE,AB-PREVerifiableoutsourcedcomputationOurtechniquesOurconstructionofAB-VPREInstantiationsSecurityanalysisAdvantagesofourAB-VPREschemesConclusions3132AdvantagesofOurAB-VPRESchemesFunctionsRe-encryptionverifiability(non-interactive)Accesscontrolupdatefromuntrustedprox