  In conventional quantum key distribution protocols, the secure key is
normally extracted from the measurement outcomes of the system. Here, a
different approach is proposed, where the secure key is extracted from the
measurement bases, rather than outcomes. Compared to the original
Bennett-Brassard-1984 protocol, the proposed protocol involves no hardware
change but modifications in data postprocessing. We show that this protocol is
more robust against detector efficiency attacks and photon-number-splitting
attacks when practical detectors and photon sources are used.
