  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.
