Differential phase shift quantum key distribution with variable loss revealing blinding and control side-channel attacks

Realistic quantum key distribution (QKD) systems suffer from side-channel attacks, which manipulate single-photon detectors. Although measurement-device-independent QKD schemes were proposed to free QKD parties (Alice and Bob) from such measurement devices, these schemes are not easy to be implemented in practice because they require precise synchronization between signals from distant parties. On the other hand, differential phase shift (DPS) QKD is a simple system for practical implementation with current optical equipment. In this study, we propose a simple modification in DPS QKD to prevent side-channel attacks (control blinding and controlling attacks) such that Bob randomly attenuates the incoming signal. This modification allows Bob to utilize photon statistics during attenuated time slots in DPS-QKD systems, using which the side-channel attacks are revealed. (C) 2019 The Japan Society of Applied Physics