「健康码」项目白皮书（英文）-苹果 谷歌-202004

ContactTracingBluetoothSpecificationPreliminary-SubjecttoModificationandExtensionApril2020Informationsubjecttocopyright.Allrightsreserved.Overview3..........................................................................................................................................................Definitions3........................................................................................................................................................ContactDetectionService3...............................................................................................................................AdvertisementPayload3....................................................................................................................................AdvertisingBehavior4........................................................................................................................................AdvertisingFlow4...............................................................................................................................................ScanningBehavior5...........................................................................................................................................ScanPowerConsiderations5.............................................................................................................................ScanningFlow5..................................................................................................................................................Privacy6.............................................................................................................................................................ContactTracingBluetoothSpecification2Informationsubjecttocopyright.Allrightsreserved.ContentsOverviewThisdocumentprovidesthedetailedtechnicalspecificationforanewprivacy-preservingBluetoothprotocoltosupportContactTracing.ContactTracingmakesitpossibletocombatthespreadoftheCOVID-19virusbyalertingparticipantsofpossibleexposuretosomeonewhotheyhaverecentlybeenincontactwith,andwhohassubsequentlybeenpositivelydiagnosedashavingthevirus. TheContactDetectionServiceisthevehicleforimplementingcontacttracingandusestheBluetoothLE(LowEnergy)forproximitydetectionofnearbysmartphones,andforthedataexchangemechanism.Definitions•ContactDetectionService-TheBLEservicefordetectingdeviceproximity.•TracingKey-Akeythatisgeneratedonceperdevice.•DailyTracingKey-AkeyderivedfromtheTracingKeyevery24hoursforprivacyconsideration.•DiagnosisKey-ThesubsetofDailyTracingKeyswhichareuploadedwhenthedeviceownerisdiagnosedpositivefortheCOVID-19virus.•RollingProximityIdentifier- AprivacypreservingidentifierderivedfromtheDailyTracingKeyandsentinthebluetoothadvertisements.Itchangesevery~15minutestopreventwirelesstrackingofthedevice.ContactDetectionServiceContactDetectionisaBLEserviceregisteredwiththeBluetoothSIGwith16-bitUUID0xFD6F,itisdesignedtoenableproximitysensingofRolling Proximity Identifierbetweendevicesforthepurposeofcomputinganexposureevent.DevicesadvertiseandscanfortheContactDetectionServicebywayofits16-bitserviceUUID.TheServiceDatatypewiththisserviceUUIDshallcontaina 128-bitRolling Proximity Identifierthatchangesperiodically.AdvertisementPayloadTheContactDetectionServicepayloadshallbeorderedasshownbelowandshallnotincludeotherdatatypes. TheContactDetectionServicepayloadhasthreesections:1.FlagsSection:LEgeneraldiscoverablemode(bit1)shallbesetto1.2.Complete16-bitServiceUUIDSection:theUUIDis0xFD6F,andshallprecedetheServiceDatasection.3.ServiceData16-bitUUIDSection:thecontentofservicedatapayloadshallbea128-bitRolling Proximity Identifier.ContactTracingBluetoothSpecification3Informationsubjecttocopyright.Allrightsreserved.AdvertisingBehavior•Advertisementsaretobenon-connectableundirectedoftypeADV_NONCONN_IND(Section2.3.1.3of5.2CoreSpec).•TheadvertiseraddresstypeshouldbeRandomNon-resolvable.•OntheplatformssupportingBluetoothRandomPrivateAddresswithrandomizedrotationtimeoutinterval,theadvertiseraddressrotationperiodshallbearandomvalue,greaterthan10minutesandlessthan20minutes.•TheadvertiseraddressandRolling Proximity IdentifiershallbechangedsynchronouslysoaddressandRolling Proximity Identifiercannotbelinked.•Aseparateadvertisinginstanceshouldbeused,ifHWallows,toprovideadvertisingreliabilityandflexibilityinchoosingoptimalinterval.•Theadvertisingintervalissubjecttochange,butiscurrentlyrecommendedtobe200-270milliseconds.AdvertisingFlowThefollowingdiagramillustratestheflowofadvertisementbetweendevices.ContactTracingBluetoothSpecification4Informationsubjecttocopyright.Allrightsreserved.ScanningBehavior•DiscoveredContactDetectionServiceadvertisementsshallbekeptonthedevice.•ScanresultsshallbetimestampedandRSSI-capturedperadvertisement.•ScanningintervalandwindowshallhavesufficientcoveragetodiscovernearbyContactDetectionServiceadvertisers within5mins.•Scanningstrategythatworksbestisopportunistic(leveragingexistingwakesandscanwindows)andwithminimumperiodicsamplingevery5mins.ScanPow