Analysis of the differential-phase-shift-keying protocol in the quantum-key-distribution system

The analysis is based on the error rate and the secure communicationrate as functions of distance for three quantum-key-distribution(QKD) protocols: the Bennett--Brassard 1984, theBennett--Brassard--Mermin 1992, and the coherentdifferential-phase-shift keying (DPSK) protocols. We consider thesecure communication rate of the DPSK protocol against an arbitraryindividual attack, including the most commonly consideredintercept-resend and photon-number splitting attacks, and concludedthat the simple and efficient differential-phase-shift-keyingprotocol allows for more than 200 km of secure communicationdistance with high communication rates.