The practical security of a continuous-variable quantum key distribution (CVQKD) system is compromised by various attack strategies. The existing countermeasures against these attacks are to exploit different real-time monitoring modules to prevent different types of attacks, which significantly depend on the accuracy of the estimated excess noise and lack a universal defense method. In this paper, we propose a defense strategy for CVQKD systems to address these disadvantages and resist most of the known attack types. We investigate several features of the pulses that would be affected by different types of attacks, derive a feature vector based on these features as the input of an artificial neural network (ANN) model, and show the training and testing process of the ANN model for attack detection and classification. Simulation results show that the proposed scheme can effectively detect most of the known attacks at the cost of reducing a small part of secret keys and transmission distance. It establishes a universal attack detection model by simply monitoring several features of the pulses without knowing the exact type of attack in advance.
There is a growing interest in the security of underwater communication with the increasing demand for undersea exploration. In view of the complex composition and special optical properties of seawater, this paper deals with a performance analysis for continuous-variable quantum key distribution (CVQKD) over an underwater link. In particular, we focus on analyzing the channel transmittance and detection efficiency based on Monte Carlo simulation for different water types, link distances and transceiver parameters. A comparison between the transmittance obtained by simple Beer’s law and Monte Carlo simulation reveals that the transmittance of underwater link may be severely underestimated in the previous underwater CVQKD research. The effect of the receiver aperture and field of view (FOV) on detection efficiency under different water types is further evaluated based on Monte Carlo. Simulation results show that the transmission distance of the underwater CVQKD system obtained by Monte Carlo simulation in pure sea water, clear ocean water and coastal ocean water is larger than that obtained by Beer’s law, while the key rate of the system in all types of water is smaller than that obtained by Beer’s law because the size and FOV of the receiver aperture are taken into account. By considering the practical system parameters, this paper establishes a comprehensive model for evaluating the security of underwater CVQKD systems with different system configurations.
Continuous-variable quantum key distribution (CVQKD) in an indoor scenario can provide secure wireless access for practical short-distance communications with high rates. However, a suitable channel model for implementing the indoor CVQKD system has not been considered before. Here, we establish an indoor channel model to show the feasibility of CVQKD in terahertz (THz) band. We adopt both active and passive state preparation schemes to demonstrate the performance of the indoor CVQKD system involving multi-path propagation. We achieve the channel transmittance characterized by frequency, water-vapor density, antenna gain, reflection loss and the surrounding itself. The ray-tracing based numerical simulations show that the multi-path propagation can degrade the performance of the indoor CVQKD system. The maximum transmission distance is two meters at 410 GHz for both active and passive state preparations, and it can be extended to 35 and 20 meters respectively by using high gain antenna to combat the multi-path propagation.
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