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

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The following protocol consists of only quantum communication in the distribution phase and only classical communication in the messaging phase. It uses the protocol for QDS with insecure channels [[Measurement Device Independent Quantum Digital Signature (MDI-QDS)#References|(1)]] and replaces KGP (Key generation protocol) with Measurement Device Independent KGP (MDI-KGP). Distribution phase can be divided into the following steps:
The following protocol consists of only quantum communication in the distribution phase and only classical communication in the messaging phase. It uses the protocol for QDS with insecure channels [[Measurement Device Independent Quantum Digital Signature (MDI-QDS)#References|(1)]] and replaces KGP (Key generation protocol) with Measurement Device Independent KGP (MDI-KGP). Distribution phase can be divided into the following steps:
*'''Key Distribution:''' Seller uses MDI-KGP twice with Buyer and Verifier, each, to generate four different [[correlated]] keys. Both Seller and Receiver have two keys each, one for message bit 0 and one for message bit 1. Sender's signature for a particular message bit is a conjugation of corresponding key for message bit sent to the Buyer and the Verifier.  
*'''Key Distribution:''' Seller uses MDI-KGP twice with Buyer and Verifier, each, to generate four different [[correlated]] keys. Both Seller and Receiver have two keys each, one for message bit 0 and one for message bit 1. Sender's signature for a particular message bit is a conjugation of corresponding key for message bit sent to the Buyer and the Verifier.  
*'''MDI-KGP:''' MDI-KGP consists of the following steps  (only quantum communication part) from MDI-QKD protocol in [[Measurement Device Independent Quantum Digital Signature (MDI-QDS)#References|(2)]]:
*'''MDI-KGP:''' MDI-KGP consists of the following steps  (only quantum communication part) from MDI-QKD protocol in [[Measurement Device Independent Quantum Digital Signature (MDI-QDS)#References|(2)]]:</br>
**''State Preparation''
The MDI-QKD protocol assumes a trusted third party, arbitrator. The following steps are performed with Seller and each recipient, pairwise.
**''Measurement''
**''State Preparation'' Seller and buyer/verifier prepare states in randomly chosen basis (from [[X, Z bases]]) and chosen intensity. These states are sent to the arbitrator
**''Sifting''
**''Measurement'' Arbitrator, if honest, performs Bell measurement on the received states. If the measurement is successful, Bell state is communicated by arbitrator 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.
**''Parameter Estimation''
**''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.
*'''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.
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