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International Conference on Computer and Communication Engineering

Feasibility of QKD over FSO link

Alma Husagic-Selman, Wajdi Fawzi Mohammed Al-Khateeb, Suhairi Saharudin

Published Jul 1, 2012• 4 citations
Publisher

Abstract

Due to the advancements in the field of quantum computing and possible compromise of existing key-exchange algorithms, it is essential to explore performance and efficiency of new key-exchange techniques, such as Quantum Key Distribution (QKD). QKD is possible over fiber cable and Free Space Optical (FSO) links. Fiber based QKD may be used if direct line of sight link is not possible, but it brings along many problems related to material properties of fiber cable and detector limitations. It is therefore more convenient to use free-space based QKD whenever physically possible. Furthermore, FSO links can be satellite-supported in order to generate worldwide distribution of quantum keys. The FSO however greatly depends on weather conditions and link length, thus it is very important to evaluate these effects on the size of quantum key. In this paper, simulation-based evaluation of FSO QKD is done given tropical weather conditions specific for Malaysia. The paper discusses how different factors, such as link distance, weather, beam intensity and transceivers setup, influence key size when BB84 QKD protocol is used. For each weather condition specific for Malaysia key size was obtained, and the percentage of the received key compared to the total generated key is calculated. The results show the size of the final encryption key after being transmitted over FSO channel influenced by various weather conditions, which implies that it is possible to use FSO based QKD in Malaysia successfully.

DOI
10.1109/iccce.2012.6271212

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Due to the advancements in the field of quantum computing and possible compromise of existing key-exchange algorithms, it is essential to explore performance and efficiency of new key-exchange techniques, such as Quantum Key Distribution (QKD). QKD is possible over fiber cable and Free Space Optical (FSO) links. Fiber based QKD may be used if direct line of sight link is not possible, but it brings along many problems related to material properties of fiber cable and detector limitations. It is therefore more convenient to use free-space based QKD whenever physically possible. Furthermore, FSO links can be satellite-supported in order to generate worldwide distribution of quantum keys. The FSO however greatly depends on weather conditions and link length, thus it is very important to evaluate these effects on the size of quantum key. In this paper, simulation-based evaluation of FSO QKD is done given tropical weather conditions specific for Malaysia. The paper discusses how different factors, such as link distance, weather, beam intensity and transceivers setup, influence key size when BB84 QKD protocol is used. For each weather condition specific for Malaysia key size was obtained, and the percentage of the received key compared to the total generated key is calculated. The results show the size of the final encryption key after being transmitted over FSO channel influenced by various weather conditions, which implies that it is possible to use FSO based QKD in Malaysia successfully.
Due to the recent rapid growth of computing technologies, today's encrypted information based on classical computational complexities will soon no longer remain secure. Quantum cryptography, or quantum key distribution (QKD), relying on the physical laws of quantum mechanics, stands out as a more powerful cryptographic solution that enables the secret key to be shared securely over publicly unsecured communication channels in the presence of eavesdroppers. QKD can be possibly implemented over both optical fiber and free-space optical (FSO) links. Compared to optical fiber, FSO has the immediate advantage of flexibility and cost-effectiveness in terms of infrastructure deployment. More interestingly, recent advancements in satellite communications using FSO links promise the future of a global QKD network for highly secure applications. This paper reviews the development of QKD over FSO for both terrestrial and satellite channels, which highlights the most up-to-date QKD protocols. Owing to how the information is encoded, different QKD protocols are classified into technology-focused categories, where their properties are reviewed and compared. The feasibility of current QKD protocols is then investigated with respect to its specific application scenarios for terrestrial and satellite FSO links, equipped with results from both theoretical and experimental studies. Based on the latest free-space QKD achievements, novel perspectives for future developments and challenges to enhance the secrecy performance and reduce implementation cost are then summarized and comprehensively discussed. The potential combination of QKD and physical layer cryptography for the newly emerging wireless mobile communications networks involved with unmanned aerial vehicles (UAV) is also introduced.
In response to the increasing demands for reliable, fast, and secure communications beyond 5G scenarios, the high-capacity networks have become a focal point. Quantum communication is at the forefront of this research, offering unmatched throughput and security. A free space optics (FSO) communication system integrated with fiber-end is designed and investigated using the Bennett–Brassard 1984 quantum key distribution (BB84-QKD) protocol. Simulation results show that reliable transmission can be achieved over a 10–15 km fiber length with a signal power of −19.54 dBm and high optical-to-signal noise of 72.28–95.30 dB over a 550 m FSO range under clear air, haze, fog, and rain conditions at a data rate of 1 Gbps. Also, the system using rectilinearly and circularly polarized signals exhibits a Stokes parameter intensity of −4.69 to −35.65 dBm and −7.7 to −35.66 dBm Stokes parameter intensity, respectively, over 100–700 m FSO range under diverse weather conditions. Likewise, for the same scenario, an FSO range of 100 m incorporating 2.5–4 mrad beam divergence provides the Stokes power intensity of −6.03 to −11.1 dBm and −9.04 to −14.12 dBm for rectilinearly and circularly polarized signals, respectively. Moreover, compared to existing works, this work allows faithful and secure signal transmission in free space, considering FSO–fiber link losses.
Abstract The establishment of a world-wide quantum communication network relies on the synergistic integration of satellite-based links and fiber-based networks. The first are helpful for long-distance communication, as the photon losses introduced by the optical fibers are too detrimental for lengths greater than about 200 km. This work aims at giving, on the one hand, a comprehensive and fundamental model for the losses suffered by the quantum signals during the propagation along an atmospheric free-space link. On the other hand, a performance analysis of different quantum key distribution (QKD) implementations is performed, including finite-key effects, focusing on different interesting practical scenarios. The specific approach that we chose allows to precisely model the contribution due to different weather conditions, paving the way towards more accurate feasibility studies of satellite-based QKD missions.
Current distance limitations of quantum key distribution (QKD) over fibre optic networks suggest that satellite (free-space optical) QKD networks will be required to enable global quantum communications. However, the operational availability of these systems is limited by background noise and strong attenuation caused by turbulence and adverse weather conditions. Using the decoy-state BB84 QKD protocol, we evaluate the secret key rate for a range of wavelengths, receiver sizes and initial beam waists through a variety of atmospheric conditions. We combine filtering techniques, adaptive optics, and wavelength selection to optimize the performance of satellite QKD. This study is simulation-based.
Free space optical (FSO) satellite communications has very attractive properties for Quantum Key Distribution (QKD). The quantum channel loss and noise are major factors in setting the maximum achievable secure key rate of QKD systems. Primarily for a LEO satellite node and the BB84 protocol a number of technologies are proposed to reduce the quantum channel loss and noise. These technologies apply to the receiver side of the QKD link, the Optical Ground Terminal. It is shown that an optical beam shaper to optimize fiber mode matching, dedicated thermo-mechanical design to reduce misalignment induced by temperature gradients and an Adaptive Optics (AO) system to counteract optical turbulence effects can result in a significant reduction of loss and background noise. A breadboard verification experiment shows that using an medium-size AO system can maintain a fiber coupling efficiency up to 40%. The developed technologies have a general applicability with respect to satellite orbit and QKD protocol used.
Next generation communications will require the exploration of alternatives to existing technologies to enable end-to-end connections for secure data exchange. 5G presents advanced connectivity opportunities even for remote rural areas. However, existing 5G platforms will benefit from complementary methods to enhance network capabilities and fulfill trust requirements. Due to high throughput data links, high-beam directivity, and energy efficiency, free-space optics (FSO) is an alternative solution with the potential to deliver high-performance and efficient security. FSO systems can be improved by adding quantum-key-distribution security to overcome advances in quantum computation. However, practical FSO quantum key distribution (FSO-QKD) requires simultaneous engineering of many elements. To oversee this requirement, the Innovate-UK project addresses the possibility of metropolitan-scale “last-mile” quantum secure connectivity through the use of free-space QKD links to support real-life use cases. In this article, we outline the design, development, and deployment of these elements within the AirQKD project.