Differential-phase-shift quantum digital signature without disclosing measurement information

A novel quantum digital signature (QDS) scheme using differential-phase-shift signal is presented. A sender broadcasts a weak coherent pulse train with 0 or pi phase to receivers, who measure its relative phases using delay interferometers with photon detectors and then employ the measurement results as authentication keys. The key distribution stage is completed with this signal transmission. Neither exchange of basis information between the sender and receivers nor exchange of a portion of a sifted key between the receivers with each other are conducted, unlike conventional QDS protocols. Therefore, our system is simpler than conventional ones. The security of the proposed scheme is discussed, and calculations evaluating system parameters to guarantee the QDS operation, such as the key length and authentication threshold, are presented.