Practical security analysis of continuous-variable quantum key distribution with unbalanced heterodyne detector

2021 ◽  
Author(s):  
Lingzhi Kong ◽  
Weiqi Liu ◽  
Fan Jing ◽  
Chen He
Keyword(s):  
Lower Bound ◽  
Quantum Key Distribution ◽  
Security Analysis ◽  
Key Distribution ◽  
Local Oscillator ◽  
Continuous Variable ◽  
Excess Noise ◽  
Secret Key ◽  
Heterodyne Detector ◽  
Practical Security

Abstract When developing practical continuous-variable quantum key distribution (CVQKD), detector is necessary at the receiver’s side.We investigate the practical security of the CVQKD system with unbalanced heterodyne detector.The result shows that unbalanced heterodyne detector introduces extra excess noise into system and decreases the lower bound of secret key rate without awareness of the legitimate communicators, which leaves loopholes for Eve to attack the system. In addition, we find that the secret key rate decreases more severely with the increase of the degree of imbalance and the excess noise induced by the imbalance is proportional to the intensity of local oscillator (LO) under the same degree of imbalance. Finally, the countermeasure is proposed to resist this kind of effects.

scholarly journals Practical Security Analysis of Reference Pulses for Continuous-Variable Quantum Key Distribution

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Wei Zhao ◽  
Ronghua Shi ◽  
Duan Huang
Keyword(s):  
Quantum Key Distribution ◽  
Beam Splitter ◽  
Security Analysis ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Secret Key ◽  
Bayesian Algorithm ◽  
Robustness To Noise ◽  
Practical Security

AbstractBy manipulating the reference pulses amplitude, a security vulnerability is caused by self-reference continuous-variable quantum key distribution. In this paper, we formalize an attack strategy for reference pulses, showing that the proposed attack can compromise the practical security of CVQKD protocol. In this scheme, before the beam splitter attack, Eve intercepts the reference pulses emitted by Alice, using Bayesian algorithm to estimate phase shifts. Subsequently, other reference pulses are re-prepared and resubmitted to Bob. In simulations, Bayesian algorithm effectively estimates the phase drifts and has the high robustness to noise. Therefore, the eavesdropper can bias the excess noise due to the intercept-resend attack and the beam splitter attack. And Alice and Bob believe that their excess noise is below the null key threshold and can still share a secret key. Consequently, the proposed attack shows that its practical security can be compromised by transmitting the reference pulses in the continuous-variable quantum key distribution protocol.

scholarly journals Sub-Gbps Key Rate Four-State Continuous-Variable Quantum Key Distribution within Metropolitan Area

2021 ◽  
Author(s):  
Heng Wang ◽  
Yang Li ◽  
Yaodi Pi ◽  
Yan Pan ◽  
Yun Shao ◽  
...  
Keyword(s):  
Metropolitan Area ◽  
Quantum Key Distribution ◽  
Security Analysis ◽  
Key Distribution ◽  
Continuous Variable ◽  
High Rate ◽  
Excess Noise ◽  
Analysis Method ◽  
Secret Key ◽  
High Efficient

Abstract Continuous-variable quantum key distribution (CVQKD) has potential advantages of high secret key rate, which is very suitable for high-speed metropolitan network application. However, the reported highest secret key rates of the CVQKD systems up to now are limited in a few Mbps. Here, we address the fundamental experimental problems and demonstrate a single-carrier four-state CVQKD with sub-Gbps key rate within metropolitan area. In the demonstrated four-state CVQKD using local local oscillator, an ultra-low level of excess noise is obtained and a high efficient post-processing setup is designed for practically extracting the final secure keys. Thus, the achieved secure key rates are 190.54 Mbps and 137.76 Mbps and 52.48 Mbps using linear channel assuming security analysis method and 233.87 Mbps, 133.6 Mbps and 21.53 Mbps using semidefinite programming security analysis method over transmission distances of 5 km, 10 km and 25 km, respectively. This record-breaking result increases the previous secret key rate record by an order of magnitude, which is sufficient to achieve the one-time pad cryptographic task. Our work shows the road for future high-rate and large-scale CVQKD deployment in secure broadband metropolitan and access networks.

scholarly journals Performance Analysis of Continuous-Variable Quantum Key Distribution with Multi-Core Fiber

2018 ◽  
Vol 8 (10) ◽  
pp. 1951 ◽  
Author(s):  
Fei Li ◽  
Hai Zhong ◽  
Yijun Wang ◽  
Ye Kang ◽  
Duan Huang ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Quantum Key Distribution ◽  
Security Analysis ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Secret Key ◽  
Quantum Communications ◽  
Core Fiber ◽  
Channel Wavelength

Performance analysis of continuous-variable quantum key distribution (CVQKD) has been one of the focuses of quantum communications. In this paper, we propose an approach to enhancing the secret rate of CVQKD with the multi-core fiber (MCF) system that transmits multiple spatial modes simultaneously. The excess noise contributed by the inter-core crosstalk between cores can be effectively suppressed by quantum channel wavelength management, leading to the performance improvement of the MCF-based CVQKD system. In the security analysis, we perform numerical simulations for the Gaussian-modulated coherent state CVQKD protocol, considering simultaneously the extra insert loss of fan-in/fan-out (FIFO), which is the extra optical device that should be used at the input and the output of the fiber. Simulation results show that the performance of the one-way and two-way protocols for each core are slightly degraded because of the insert loss of the FIFO, but the total secret key rate can be increased, whereas the performance of the measurement-device-independent CVQKD protocol will be degraded due to the effect of the insert loss of the FIFO. These results may provide theoretical foundation for the space-division multiplexing CVQKD system.

scholarly journals Security Analysis of Discrete-Modulated Continuous-Variable Quantum Key Distribution over Seawater Channel

2019 ◽  
Vol 9 (22) ◽  
pp. 4956 ◽  
Author(s):  
Xinchao Ruan ◽  
Hang Zhang ◽  
Wei Zhao ◽  
Xiaoxue Wang ◽  
Xuan Li ◽  
...  
Keyword(s):  
Quantum Key Distribution ◽  
Secure Communication ◽  
Security Analysis ◽  
Finite Size ◽  
Key Distribution ◽  
Continuous Variable ◽  
Heterodyne Detection ◽  
Secret Key ◽  
Transmission Distance ◽  
Better Than

We investigate the optical absorption and scattering properties of four different kinds of seawater as the quantum channel. The models of discrete-modulated continuous-variable quantum key distribution (CV-QKD) in free-space seawater channel are briefly described, and the performance of the four-state protocol and the eight-state protocol in asymptotic and finite-size cases is analyzed in detail. Simulation results illustrate that the more complex is the seawater composition, the worse is the performance of the protocol. For different types of seawater channels, we can improve the performance of the protocol by selecting different optimal modulation variances and controlling the extra noise on the channel. Besides, we can find that the performance of the eight-state protocol is better than that of the four-state protocol, and there is little difference between homodyne detection and heterodyne detection. Although the secret key rate of the protocol that we propose is still relatively low and the maximum transmission distance is only a few hundred meters, the research on CV-QKD over the seawater channel is of great significance, which provides a new idea for the construction of global secure communication network.

scholarly journals Demonstration of high-speed and low-complexity continuous variable quantum key distribution system with local local oscillator

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shengjun Ren ◽  
Shuai Yang ◽  
Adrian Wonfor ◽  
Ian White ◽  
Richard Penty
Keyword(s):  
Distribution System ◽  
Repetition Rate ◽  
Quantum Key Distribution ◽  
Optimization Technique ◽  
Key Distribution ◽  
Local Oscillator ◽  
Continuous Variable ◽  
Noise Model ◽  
System Level ◽  
Excess Noise

AbstractWe present an experimental demonstration of the feasibility of the first 20 + Mb/s Gaussian modulated coherent state continuous variable quantum key distribution system with a locally generated local oscillator at the receiver (LLO-CVQKD). To increase the signal repetition rate, and hence the potential secure key rate, we equip our system with high-performance, wideband devices and design the components to support high repetition rate operation. We have successfully trialed the signal repetition rate as high as 500 MHz. To reduce the system complexity and correct for any phase shift during transmission, reference pulses are interleaved with quantum signals at Alice. Customized monitoring software has been developed, allowing all parameters to be controlled in real-time without any physical setup modification. We introduce a system-level noise model analysis at high bandwidth and propose a new ‘combined-optimization’ technique to optimize system parameters simultaneously to high precision. We use the measured excess noise, to predict that the system is capable of realizing a record 26.9 Mb/s key generation in the asymptotic regime over a 15 km signal mode fibre. We further demonstrate the potential for an even faster implementation.

scholarly journals SECURITY OF A NEW TWO-WAY CONTINUOUS-VARIABLE QUANTUM KEY DISTRIBUTION PROTOCOL

2012 ◽  
Vol 10 (05) ◽  
pp. 1250059 ◽  
Author(s):  
MAOZHU SUN ◽  
XIANG PENG ◽  
YUJIE SHEN ◽  
HONG GUO
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Noisy Channel ◽  
Quantum Channels ◽  
Secret Key ◽  
Transmission Distance ◽  
The Family ◽  
The One

The original two-way continuous-variable quantum-key-distribution (CV-QKD) protocols [S. Pirandola, S. Mancini, S. Lloyd and S. L. Braunstein, Nat. Phys. 4 (2008) 726] give the security against the collective attack on the condition of the tomography of the quantum channels. We propose a family of new two-way CV-QKD protocols and prove their security against collective entangling cloner attacks without the tomography of the quantum channels. The simulation result indicates that the new protocols maintain the same advantage as the original two-way protocols whose tolerable excess noise surpasses that of the one-way CV-QKD protocol. We also show that all sub-protocols within the family have higher secret key rate and much longer transmission distance than the one-way CV-QKD protocol for the noisy channel.

Practical security analysis of continuous-variable quantum key distribution with jitter in clock synchronization

2018 ◽  
Vol 382 (12) ◽  
pp. 811-817 ◽  
Author(s):  
Cailang Xie ◽  
Ying Guo ◽  
Qin Liao ◽  
Wei Zhao ◽  
Duan Huang ◽  
...  
Keyword(s):  
Quantum Key Distribution ◽  
Clock Synchronization ◽  
Security Analysis ◽  
Key Distribution ◽  
Continuous Variable ◽  
Practical Security

DISCRETELY MODULATED CONTINUOUS-VARIABLE QUANTUM KEY DISTRIBUTION WITH A NONDETERMINISTIC NOISELESS AMPLIFIER

2013 ◽  
Vol 11 (04) ◽  
pp. 1350037 ◽  
Author(s):  
JIAN FANG ◽  
YUAN LU ◽  
PENG HUANG ◽  
GUANGQIANG HE ◽  
GUIHUA ZENG
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Secret Key ◽  
Transmission Distance ◽  
Linear Amplifier ◽  
Detection Stage ◽  
Maximum Transmission ◽  
Better Than

In this paper, we first study a generalized protocol of discrete modulation for continuous-variable quantum key distribution with N coherent states in a Gaussian lossy and noisy channel and investigate its performance against collective attacks. We find that discrete modulation protocols with more than eight states do not perform better than the eight-state protocol. Then, we study the improvement of this protocol by using a nondeterministic noiseless linear amplifier (NLA) on Bob's detection stage. Results indicate that a NLA with gain g can extend the maximum transmission distance by 50 log 10g2 km and can increase the maximal tolerable excess noise. With the reconciliation efficiency β, we find the gain of NLA has a maximal value defined as g max and by adjusting the gain to about βg max one can have the best improvement on secret key rate.

scholarly journals Practical Security Bounds against Trojan Horse Attacks in Continuous-Variable Quantum Key Distribution

2020 ◽  
Vol 10 (21) ◽  
pp. 7788
Author(s):  
Yaxi Pan ◽  
Ling Zhang ◽  
Duan Huang
Keyword(s):  
Quantum Key Distribution ◽  
Information Leakage ◽  
Bright Light ◽  
Key Distribution ◽  
Continuous Variable ◽  
Trojan Horse ◽  
Excess Noise ◽  
Secret Key ◽  
Real Component ◽  
Light Pulses

As the existence of non-zero reflection coefficients in the real component of continuous-variable quantum key distribution (CV-QKD) systems, Eve can probe the system by sending the bright light pulses into Alice’s set-up. With the analysis of back-reflections, Eve only takes a few back-reflected photons to intercept information and obtain the raw key bit. In this paper, the attack problems are converted into the information leakage problems. First, we analyzed the Trojan horse attacks with different wavelengths and confirmed its side effects, such as crosstalk and anti-Stokes Raman scattering, by a numerical simulation. Then, based on the wavelength-dependent property of beam splitter, we presented a practical way to estimate the deviation of shot noise and therefore correct the excess noise by inserting different wavelength pulses under joint attacks. Finally, we specified the security bounds of the system through quantifying the excess noise bounds caused by the Trojan horse attacks and provided a theoretical reference for the secret key transmission of system. As a consequence, the transmission errors within the security bounds can be negligible and the legitimate users will not perceive the presence of Eve.

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