Measurement Device Independent Quantum Digital Signature (MDI-QDS): Difference between revisions

Measurement Device Independent Quantum Digital Signature (MDI-QDS) (edit)

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 **'''State Preparation:'''Seller and buyer/verifier prepare states in randomly chosen basis and randomly chosen intensity. These states are sent to the arbitrator
 **'''Measurement:'''Arbitrator, if honest, performs Bell measurement on the received states. If the measurement is successful, Bell state is communicated by arbitrator to  over public channel.
-**'''Sifting:'''Seller and buyer/verifier exchange the information regarding the intensity and basis used to prepare states, in case of successful Bell measurement. These states are grouped into two sets, depending on the basis used for preparation. The above steps are repeated until the cardinality of both sets is more than required threshold number of elements for each set. In the end, Buyer/Verifier flips part of his bits according to the [[Measurement Device Independent Quantum Digital Signature (MDI-QDS)#Pseudo Code|Pseudo code]] given below.
+**'''Sifting:''' In case of successful Bell measurement, Seller and buyer/verifier exchange the information regarding the intensity and basis used to prepare states over authenticated quantum channel. Otherwise they discard their data. The data corresponding to successful measurements are grouped into two sets, depending on the basis used for preparation. The above steps are repeated until the cardinality of both sets is more than required threshold number of elements for each set. In the end, Buyer/Verifier flips his bits in his two sets according to the Bell state obtained in each case (given in [[Measurement Device Independent Quantum Digital Signature (MDI-QDS)#Pseudo Code|Pseudo code]] below).
 **'''Parameter Estimation:'''
 *'''Symmetrisation:''' Buyer and Verifier exchange half of their randomly chosen eliminated signature elements. This prevents a dishonest seller succeed in cheating by sending dissimilar public keys to the receiver and makes the protocol secure against repudiation. Thus ends the distribution phase.