In IoT, smart sensors enable data collection, real-time monitoring,
decision-making, and automation, but their proliferation exposes them to
cybersecurity threats. Zero Trust Architecture enhances IoT security by
challenging conventional trust models and emphasizing continuous trust
verification in the overall \875.0billionIoTmarketprojectedby2025.Thispaperpresentsanewzero−trustreal−timelightweightaccesscontrolprotocolforCloud−centricdynamicIoTsensornetworks.Thisprotocolempowersdataowners,referredtoassensorcoordinators,todefineintricateaccesspolicies,blendingrecipientidentifiersanddata−relatedattributesfordataencryption.Additionally,theprotocolincorporatesefficientcryptographicprimitives,eliminatingtheneedforrelianceonatrustedparty.Furthermore,itensuresreal−timedataaccesswhilepreservingdataconfidentialityanduserprivacythroughseamlessdatauploadtothecloudandtheoffloadingofcomputationallyintensivetasksfromresource−constraineddataownersandsensors.TheprotocolutilizesMerkleTreesforlightweight,ongoingtrustmeasurementofsensors,ensuringefficienttrustassessmentbysensorcoordinators.Simultaneously,thecloudconductsthoroughtrustevaluationsfornetworkentitiesincludingusers.Comprehensivesecurityanalysisandperformanceevaluationhighlighttheprotocol′seffectivenessintacklingthemultifacetedsecuritychallengesofIoTecosystemswhileensuringscalabilityandhighavailability.