  In the original round-robin differential-phase-shift (RRDPS) quantum key
distribution and its improved method, the photon-number-resolving detectors are
must for the security. We present a RRDPS protocol with yes-no detectors only.
We get the upper bounds of mutual information of Alice and Eve, and Bob and
Eve, and the formula of key rate. Our main idea is to divide all counts into
two classes, the counts due to the odd number photons of incident detectors and
the counts due to the even number photons of incident detectors. The fact that
the bit-flip error rate of the later class is certainly $50\%$ makes it
possible for us to perform a tightened estimation of the upper bound of the
leakage information. The robustness of original RRDPS against source flaws such
as side-channel attacks still holds for the RRDPS with yes-no detectors. The
simulation results show that the key rate of RRDPS with yes-no detectors is
close to that of RRDPS with photon-number-resolving detectors. Our results make
the RRDPS protocol much more practical.
