Practical DPS-QKD distance limited by sequential attacl

Takuya Ikuta

Muataz Alhussein, Kyo Inoue

Toshitatsu Yamamoto

Kukita, Takada, Inoue

Hiroki Kawahara, Toru Oka, Kyo Inoue

Phase-modulated differential-phase-shift (DPS) quantum key distribution (QKD) is presented for combating sequential attacks that most severely restrict the DPS-QKD system distance. Slow phase modulation imposed onto the DPS signal obstructs the optimum unambiguous state discrimination measurement conducted in the sequential attack and improves the QKD distance as a result. The condition with which the phase modulation does not degrade the DPS-QKD system performance is also described.

Marcos Curty, Kiyoshi Tamaki, Tobias Moroder

We investigate limitations imposed by detector dead times on the performance of sequential attacks against a differential-phase-shift (DPS) quantum key distribution (QKD) protocol with weak coherent pulses. In particular, we analyze sequential attacks based on unambiguous state discrimination of the signal states emitted by the source and we obtain ultimate upper bounds on the maximal distance achievable by a DPS QKD scheme both for the case of calibrated and uncalibrated devices, respectively.