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International Conference on Optical Communications and Networks (ICOCN)

Continuous Variable Quantum Key Distribution Based Encryption Method for Free-Space Optical Communication Systems

Xi Feng Fang, Jianping Li, Yi Yan, Yuxiang Liu, SiLu Fan

Published Jul 28, 2025• 1 citation
Publisher

Abstract

In this paper, we have investigated the application of continuous-variable quantum key distribution (CV-QKD) systems to provide keys for the AES-CTR algorithm. Constellation diagrams and bit error rates were used to visually demonstrate the impact of free-space optical (FSO) communication channels on the signal. Simulation results demonstrated that this method improve the security of FSO system evidently

DOI
10.1109/icocn67308.2025.11145638

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IEEE photonics journal•Oct 11, 2018•28 citations
In this paper, we have investigated the application of continuous-variable quantum key distribution (CV-QKD) systems to provide keys for the AES-CTR algorithm. Constellation diagrams and bit error rates were used to visually demonstrate the impact of free-space optical (FSO) communication channels on the signal. Simulation results demonstrated that this method improve the security of FSO system evidently
Quantum key distribution (QKD) provides secure keys with information-theoretic security ensured by the principles of quantum mechanics. The flexibility and efficient deployment of free-space optical (FSO) quantum key distribution systems can make them highly advantageous. Despite the benefits of free-space transmission, there is still a chance of running into unfavorable weather conditions like fog. According to this study, free-space continuous variable (CV) QKD systems may be applicable when fog is present. Using attenuation based on the Kim and Kruse empirical visibility models, the performance of the models that explain the relationship between fog attenuation and air visibility is examined in order to evaluate its impact on the secure key rate (SKR) at wavelengths of 850 and 1550 nm. A comparative analysis between the two wavelengths is carried out to highlight their suitability under different weather conditions. Based on the results, 1550 nm performs better in foggy situations, reaching an SKR of 1.389379 bits/symbol, because of lower scattering losses, whereas 850 nm achieves a longer range of 12 km in clear air because of smaller diffraction divergence. The results demonstrate that wavelength selection plays a critical role in enhancing the robustness of CV-QKD systems that operate over FSO links. In addition, optimizing reconciliation efficiency (β) under thick-fog conditions greatly improved the SKR, indicating that 1550 nm operation has the ability to achieve reliable and secure quantum communication. Results show that varying β from 0.90 to 1.00 for both 850 nm and 1550 nm produces SKR enhancement of (0.63-0.80 bits/symbol) and (0.97-1.13 bits/symbol), respectively.
Satellite QKD/FSO systems, which facilitate quantum key distribution (QKD) over free-space optical (FSO) links between satellites and ground stations, present a promising pathway toward achieving global security in upcoming sixth-generation (6G) wireless communications. Our study focuses on a superior type of these systems, the satellite EB/CV-QKD/FSO, which utilizes the continuous-variable (CV) method for quantum state representation and the entanglement-based (EB) scheme for QKD implementation. We propose the use of optical phase-shift keying (QPSK) signaling and dual-threshold/heterodyne detection (DT/HD) receivers to bolster the reliability and feasibility of satellite EB/CV-QKD/FSO systems. Closed-form expressions for key system performance metrics are derived using improved channel modeling. Numerical results are presented to showcase the effects of channel impairments on the system performance. We also provide recommendations for optimal system setup parameters, aiming to enhance performance.
This paper studies a multiple-input multiple-output (MIMO) free-space optical (FSO) communication system employing continuous-variable quantum key distribution (CV-QKD), with the goal to support secret key transmission between two legitimate users, Alice and Bob. All involved wireless channels are subjected to atmospheric turbulence leading to beam spreading, pointing error, and turbulence-induced fading, which along with the presence of hybrid quantum noise negatively impact secret key exchange. Furthermore, the legitimate MIMO FSO system faces the threat of compromise from an eavesdropper, Eve, employing a collective Gaussian attack to intercept the secret key exchange. Novel one- and two-way protocols for enhancing the security of the transmitted keys are proposed. To this end, the transmissivity of the FSO channels is mathematically formulated and bounds on the mutual information between the transmitted and received coherent states are obtained, which are then used for deriving novel expressions for the secret key rates (SKRs) for both one- and two-way protocols. The presented numerical results corroborate the proposed analytical secrecy framework, quantifying the SKR gains obtained by employing MIMO and the two-way protocol for FSO CV-QKD systems.
A network system's credibility is highly dependent on its resistance to cyber-attacks. With the advent of quantum computers, the security of traditional network systems is compromised since most of the networking systems rely on the difficulty of factoring out the prime factors which can be easily done with Shor's algorithm with the help of quantum computers. Another advantage of Quantum Key Distribution (QKD) over the traditional cryptographic system is that any attempt to eavesdrop the data introduces anomalies due to the Heisenberg uncertainty principle and the no-cloning theorem. The authors propose a Continuous Variable-QKD (CV-QKD) system where the information is encoded in the same coherent state of light that can be detected through homodyne or heterodyne detection which is compatible with standard telecom components. This CV-QKD system also has an authentication layer and a classical channel. But in this paper, we mainly focus on the quantum channel and the efficiency of using channel estimation in FSO which supposedly gives a better output values than traditional Digital Signal Processing (DSP) with equalization (Linear Interpolation). Metrics such as Mean Square Error (MSE) is used to measure the efficiency of the system.
Continuous-variable quantum key distribution (CV-QKD) has been proposed as a method for securely exchanging keys to protect against the security concerns caused by potential advancements in quantum computing. In addition to optical fibre transmission, the free-space optical (FSO) channel is an interesting channel for CV-QKD, as it is possible to share keys over this channel wirelessly. The instability of the FSO channel caused by turbulence-induced fading, however, can cause a degradation in the system's performance. One of the most important aspects of CV-QKD is the reconciliation step, which significantly impacts the performance of the CV-QKD system. Hence, rate-adaptive reconciliation is necessary for CV-QKD over FSO to combat the fluctuations in the channel and improve secret key rates (SKRs). Therefore, in this paper, we simulate the impact of discrete modulation on the reconciliation efficiency and consider the use ofddd-dimensional reconciliation withd>8d > 8d>8to mitigate this impact, improving reconciliation efficiencies by up to 3.4%. We validate our results by experimentally demonstrating CV-QKD over a turbulent FSO link and demonstrate SKR gains by up to 165%. Furthermore, we optimise the reconciliation efficiency for FSO links, achieving additional SKR gains of up to 7.6%.
We propose and experimentally investigate a high-speed Kramers-Kronig (KK) scheme based continuous-variable quantum key distribution (CV-QKD) system over a free-space optical (FSO) channel. The atmospheric turbulence channel is emulated by three spatial light modulators on which three randomly generated azimuthal phase patterns yielding Andrews' spectrum are recorded. The proposed KK scheme enables a low-complexity implementation, insensitivity to laser phase noise, low detection noise, and accurate channel transmittance monitoring. In addition, eight state CV-QKD protocols and 10-channels wavelength-division multiplexing (WDM) scheme are experimentally verified to obtain a high secure key rate. In our experiment, the minimum transmittance of 0.6 is required to guarantee the secure transmission, and a total SKR of 2.1 Gb/s can be obtained at the mean transmittance in weak turbulence regime.