Quantum key distribution (QKD) is a promising technique to resist the threat against quantum computers. However, the high loss of quantum signals over a long-distance optical fiber is an obstacle for QKD in the intercontinental domain. In this context, the quantum satellite network is preferred over the terrestrial quantum optical network. Due to the mobility of satellites, the satellite topology is dynamic in the quantum satellite network, which remains a challenge for routing. In hybrid geostationary-earth-orbit (GEO)/low-earth-orbit (LEO) quantum satellite networks, the lack of an efficient scheduling scheme for GEO/LEO satellites also limits the construction of quantum satellite networks. Therefore, this paper provides a topology abstraction-based routing scheme for secret-key provisioning, where the dynamic physical topology is translated into a quasi-static abstracted topology. This scheme contributes to saving the precious secret key resources. In order to improve the success probability of long-distance QKD requests, three novel resource-scheduling heuristic algorithms are proposed in hybrid GEO/LEO quantum satellite networks. Simulation results indicate that the proposed algorithms can improve the success probability of QKD requests by 47% compared to the benchmark.
Quantum key distribution (QKD) is a promising technique to resist the threat against quantum computers. However, the high loss of quantum signals over a long-distance optical fiber is an obstacle for QKD in the intercontinental domain. In this context, the quantum satellite network is preferred over the terrestrial quantum optical network. Due to the mobility of satellites, the satellite topology is dynamic in the quantum satellite network, which remains a challenge for routing. In hybrid geostationary-earth-orbit (GEO)/low-earth-orbit (LEO) quantum satellite networks, the lack of an efficient scheduling scheme for GEO/LEO satellites also limits the construction of quantum satellite networks. Therefore, this paper provides a topology abstraction-based routing scheme for secret-key provisioning, where the dynamic physical topology is translated into a quasi-static abstracted topology. This scheme contributes to saving the precious secret key resources. In order to improve the success probability of long-distance QKD requests, three novel resource-scheduling heuristic algorithms are proposed in hybrid GEO/LEO quantum satellite networks. Simulation results indicate that the proposed algorithms can improve the success probability of QKD requests by 47% compared to the benchmark.
Quantum key distribution (QKD) has attracted much attention on secure communications across global networks. QKD over satellite networks can overcome the limitations of terrestrial optical networks, such as large attenuation over long distance fiber channel and difficulty of intercontinental domain communications. Different QKD networks (around the world) can intercommunicate through quantum satellites, leading to a global quantum network in near future. This raises a new resource allocation and management problem of QKD involving multiple satellite layers and distributed ground stations. Using existing schemes, a single satellite cannot perform QKD for ground stations for the whole day. Moreover, the research problem is more challenging due to limitations of satellite coverage: limited cover time of low earth orbit (LEO) satellite, high channel losses of geostationary earth orbit (GEO) satellite, etc. To overcome these limitations, our study proposes a double-layer quantum satellite network (QSN) implemented quantum key pool (QKP) to relay keys for ground stations. We propose a new architecture of trusted-repeater-based double-layer quantum satellite networks, comprising GEO and LEO satellites. We also address the routing and key allocation (RKA) problem for key-relay services over QSNs. We propose a novel joint GEO-LEO routing and key allocation (JGL-RKA) algorithm to solve the RKA problem. Simulative results show that the proposed scheme can increase success probability of key-relay services significantly. We also present the impact of different route selections mechanisms, number of satellite links, satellite node capability, and service granularity on network performance.
Free-space long-distance quantum key distribution (QKD) has the characteristics of low attenuation and wide coverage, which can overcome the limitation of transmission distance based on ground optical fiber QKD networks. Long-distance QKD requests can be relayed by quantum satellites to achieve intercontinental QKD. At present, there is only one quantum satellite in space, quantum satellite network with multiple quantum satellites is necessary to be deployed to cover the global. Thus, how to construct the quantum satellite network becomes a new challenge. In this paper, we propose a centralized and distributed collaborative scheme of quantum satellite network. Low-Earth-orbit (LEO) quantum satellites, as important relay satellites, will affect the performance of the global QKD network. Based on the above architecture, we analyze the influence of the structure of LEO quantum satellite constellation on the QKD performance. Simulation results show that the key relay performance of the constellation is related to the form of inter-satellite link. and the more the number of satellites is, the greater the successful probability of the key relay services will be.
Quantum Key Distribution (QKD) is a technology that enables the exchange of private encryption keys between two legitimate parties, using protocols that involve quantum mechanics principles. The rate at which secret keys can be exchanged depends on the attenuation that is experienced. Therefore, it is more convenient to replace many terrestrial fiber segments (and repeaters) by just few optical satellite links that would enable flexible global coverage. Then, the satellite nodes can take the role of trusted-relays, forwarding the secret keys from source to destination. However, since the rate at which secret keys can be generated in each quantum link is limited, it is very important to select the intermediate satellite nodes to inter-connect ground stations efficiently. This paper studies the most convenient allocation of resources in a QKD network that combines complementary connectivity services of GEO and LEO satellites. The aim of the centralized routing algorithm is to select the most convenient trusted-relays to forward the secret keys between pairs of ground stations, verifying the constraints that satellite-to-ground and inter-satellite quantum channels have.
With the rapid advancement of Low Earth Orbit (LEO) satellite constellations, ensuring the security of satellite-to-ground communication has become a critical concern. Traditional cryptographic techniques, while effective against classical attacks, face increasing threats from quantum computing. This paper proposes a quantum key secure transmission method tailored for LEO satellite-ground communication scenarios. The method integrates quantum key distribution (QKD) with dynamic channel estimation and orbital mobility prediction to support secure and low-latency key handshakes between satellites and ground stations. A hybrid encryption strategy is introduced, where QKD-generated keys are used to refresh symmetric session keys in real time, significantly enhancing resistance to eavesdropping and man-in-the-middle attacks. Simulation results demonstrate that the proposed method ensures stable key distribution under Doppler-shifted and intermittent link conditions, achieving improved secrecy capacity and resilience against quantum-level adversaries. This work provides a viable and scalable quantum-safe communication solution for future secure satellite networks.
Satellite-based quantum key distribution (QKD), especially relying on low Earth orbit (LEO) satellites, overcomes the geographical limitations of fiber-based QKD and enables global secure communications. However, existing QKD link establishment schemes for LEO quantum satellite networks fail to fully consider practical scenarios (e.g., multi-layer constellations as well as heterogeneous satellite–ground and inter-satellite QKD links) along with realistic constraints (e.g., different illumination conditions and the need to avoid frequent link switching). To address this gap, this work focuses on the adaptive establishment of satellite–ground and inter-satellite QKD links in single- and dual-layer LEO quantum satellite networks. We describe the network structures of single- and dual-layer constellations, as well as formulate the corresponding network model, secret key rate model, and secret key volume model. To realize adaptive QKD link establishment, we develop two integer linear programming (ILP) models and design three heuristic algorithms. The two ILP models are denoted as ILP-G and ILP-R, respectively, where ILP-G aims to maximize the generated key volume, and ILP-R is dedicated to optimizing global key resource balance by prioritizing QKD links with lower remaining key volume. The three heuristic algorithms are designed based on maximum key rate (MaxKR), maximum generated key volume (MaxGKV), and minimum remaining key volume (MinRKV). Simulation results verify the applicability of the proposed approaches across single- and dual-layer LEO quantum satellite networks. Comparative evaluations against two benchmarks, i.e., random fit (RF) and first fit (FF), show that ILP-G and MaxGKV achieve the largest cumulative key volume, while ILP-R and MinRKV outperform the other approaches in key volume distribution, quantum satellite availability, and total number of established QKD links. Specifically, the cumulative key volume of ILP-G is 44.0% and 33.8% higher than that of RF in single- and dual-layer LEO quantum satellite networks, respectively. Furthermore, the dual-layer constellation generates more key resources, with the cumulative key volume reaching approximately five times that of the single-layer constellation. It also exhibits a more balanced global key resource distribution, where key resources are distributed across a broader set of node pairs rather than concentrated on a limited subset of nodes.
Quantum key resources in quantum satellite networks are fundamental to confidential data forwarding, which highly depends on the network topology. In this paper, we propose a network topology construction scheme via formulating the dynamic link establishment among network nodes as an integer linear programming to maximize the number of available quantum keys in the topology. Then we solve this topology optimization problem through subgradient method based on the Lagrange duality theory. Under the optimized topology, we further propose a key-based routing and resource allocation (KRRA) algorithm to forward secret keys for ground stations. The simulation results show that our scheme performs better than the benchmark method with the minimum route distance in terms of the number of quantum keys and the success probability of real-time secret key forwarding service.