Recently,Liuetal.[Commun.Theor.Phys.57(2012)583]proposedaquantumprivatecomparisonprotocolbasedonentanglementswappingofBellstates,whichaimstosecurelycomparetheequalityoftwoparticipants’informationwiththehelpofasemi-honestthirdparty(TP).However,thepresentstudypointsoutthereisafatalloopholeinLiuetal.’sprotocol,andTPcanmakeBell-basismeasurementtoknowalltheparticipants’secretinputswithoutbeingdetected.Tofixtheproblem,asimplesolution,whichusesone-timeeavesdroppercheckingwithdecoyphotonsinsteadoftwiceeavesdroppercheckingwithBellstates,isdemonstrated.Comparedwiththeoriginalprotocol,itnotonlyreducestheBellstatesconsumptionbutalsosimplifiestheprotocolsteps.
