Trustworthiness of measurement devices in round-robin differential-phase-shift quantum key distribution

Abstract

Round-robin differential-phase-shift quantum key distribution (RRDPS QKD) has been proposed to raise the noise tolerability of the channel. However, in practice, the measurement device in RRDPS QKD may be imperfect. Here, we show that, with these imperfections, the security of RRDPS may be damaged, by proposing two attacks for RRDPS systems with uncharacterized measurement devices. One is valid even for a system with unit total efficiency, while the other is valid even when a single photon state is sent. To prevent these attacks, either security arguments need to be fundamentally revised or further practical assumptions on the measurement device should be put.