Maintaining security against photon-number-splitting attacks in subcarrier wave quantum communication systems

Yoshifumi Nishida, Hidenori Kuwakado, Masakatu Morii +1 more

陈彦 Chen Yan, 杨红宇 Yang Hongyu, 邓科 Deng Ke

Dmitry Anatolevich Kronberg

Coherent state quantum cryptography protocols are of interest due to their easy implementation. However, the security proof of such protocols against all attacks can be tricky because of the attenuation in the communication channel that can be exploited by an eavesdropper. In this work, an attack on the subcarrier wave quantum cryptography protocol has been built, which generalizes the photon number splitting attack. The efficiency of the attack has been analyzed, in particular, for the case where the eavesdropper does not have quantum memory.

Andrei Gaidash, Козубов Антон Владимирович, V. I. Egorov +1 more

Subcarrier wave quantum key distribution systems demonstrate promising capabilities for secure quantum networking. However for this class of devices no implementation of secure decoy states protocol was developed. It leaves them potentially vulnerable to photon-number splitting attacks on quantum channel and limiting the key distribution distance. We propose a practical solution to this problem by calculating the required parameters of light source and modulation indices for signal and decoy states in a subcarrier wave system and describing the corresponding experimental scheme.

Darsh Shani, Vishwas Vedantham, Prachi Shah +1 more

G. P. Miroshnichenko, Козубов Антон Владимирович, A. A. Gaidash +2 more

We consider a subcarrier wave quantum key distribution (QKD) system, where quantum encoding is carried out at weak sidebands generated around a coherent optical beam as a result of electro-optical phase modulation. We study security of two protocols, B92 and BB84, against one of the most powerful attacks for this class of systems, the collective beam-splitting attack. Our analysis includes the case of high modulation index, where the sidebands are essentially multimode. We demonstrate numerically and experimentally that a subcarrier wave QKD system with realistic parameters is capable of distributing cryptographic keys over large distances in presence of collective attacks. We also show that BB84 protocol modification with discrimination of only one state in each basis performs not worse than the original BB84 protocol in this class of QKD systems, thus significantly simplifying the development of cryptographic networks using the considered QKD technique.