Round-robin differential-phase-shift quantum key distribution (RRDPS QKD) hasbeen proposed to raise the noise tolerability of the channel. However, inpractice, the measurement device in RRDPS QKD may be imperfect. Here, we showthat, with these imperfections, the security of RRDPS may be damaged, byproposing two attacks for RRDPS systems with uncharacterized measurementdevices. One is valid even for a system with unit total efficiency, while theother is valid even when a single photon state is sent. To prevent theseattacks, either security arguments need to be fundamentally revised or furtherpractical assumptions on the measurement device should be put.
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