Space-air-ground integrated networks (SAGIN) are one of the most promising advanced paradigms in the sixth generation (6G) communication. SAGIN can support high data rates, low latency, and seamless network coverage for interconnected applications and services. However, communications in SAGIN are facing tremendous security threats from the everincreasing capacity of quantum computers. Fortunately, quantum key distribution (QKD) for establishing secure communications in SAGIN, i.e., QKD over SAGIN, can provide information-theoretic security. To minimize the QKD deployment cost in SAGIN with heterogeneous nodes, in this paper, we propose a resource allocation scheme for QKD over SAGIN using stochastic programming. The proposed scheme is formulated via two-stage stochastic programming (SP), while considering uncertainties such as security requirements and weather conditions. Under extensive experiments, the results clearly show that the proposed scheme can achieve the optimal deployment cost under various security requirements and unpredictable weather conditions.
Space-air-ground integrated networks (SAGIN) are one of the most promising advanced paradigms in the sixth generation (6G) communication. SAGIN can support high data rates, low latency, and seamless network coverage for interconnected applications and services. However, communications in SAGIN are facing tremendous security threats from the everincreasing capacity of quantum computers. Fortunately, quantum key distribution (QKD) for establishing secure communications in SAGIN, i.e., QKD over SAGIN, can provide information-theoretic security. To minimize the QKD deployment cost in SAGIN with heterogeneous nodes, in this paper, we propose a resource allocation scheme for QKD over SAGIN using stochastic programming. The proposed scheme is formulated via two-stage stochastic programming (SP), while considering uncertainties such as security requirements and weather conditions. Under extensive experiments, the results clearly show that the proposed scheme can achieve the optimal deployment cost under various security requirements and unpredictable weather conditions.
In the upcoming 6G era, existing ground networks have evolved toward space-air-ground integrated networks (SAGIN), providing ultra-high data rates, seamless network coverage, and ubiquitous intelligence for communications of applications and services. However, conventional communications in SAGIN still face data confidentiality issues. Fortunately, the concept of Quantum Key Distribution (QKD) over SAGIN is able to provide information-theoretic security for secure communications in SAGIN with quantum cryptography. Therefore, in this article, we propose quantum-secured SAGIN (Q-SAGIN) which are feasible to achieve proven secure communications using quantum mechanics to protect data channels between space, aerial, and ground nodes. Moreover, we propose a universal QKD service provisioning framework to minimize the cost of QKD services under the uncertainty and dynamics of communications in Q-SAGIN. In this framework, fiber-based QKD services are deployed in passive optical networks with the advantages of low loss and high stability. Moreover, the widely covered and flexible satellite-and UAV-based QKD services are provisioned as a supplement during the real-time data transmission phase. Finally, to examine the effectiveness of the proposed concept and framework, a case study of Q-SAGIN in the Metaverse is conducted where uncertain and dynamic factors of the secure communications in Metaverse applications are effectively resolved in the proposed framework.
Federated learning (FL) is a distributed machine learning paradigm with a promising future, which can preserve data privacy while training the global model collaboratively. However, FL is still facing model confidentiality issues. Therefore, in this paper, we propose a quantum key distribution (QKD) based secure FL scheme to facilitate FL model encryption against network eavesdropping attacks. Specifically, we introduce a stochastic resource allocation scheme for QKD to support FL networks. In the network, remote FL workers are connected to the server to train an aggregated global model in a distributed manner. However, due to the unpredictable number of workers at each location, the demand for secret-key rates to support secure model transmission to the server is not uniform. The proposed scheme can allocate QKD resources (i.e., wavelengths) in a way that minimizes the total cost given the stochastic demand. We formulate the optimization problem for the proposed scheme as a stochastic programming model. Numerical results demonstrate that the proposed scheme can successfully achieve the cost-minimizing objective while satisfying all uncertain demands and other security constraints.
Quantum Key Distribution (QKD) is a foundational technology for future secure communications, and several QKD networks have been already deployed and tested around the world using optical fibers. However, these networks cannot scale in size due to the inefficiency of fiber QKD networks with increasing distances, making satellite networks a major candidate for long-distance QKD networks. In satellite QKD networks, satellites and ground stations can act as trusted relays, distributing keys between satellite-ground station pairs to serve requests among ground stations. Satellite QKD networks face fundamental challenges due the time-varying nature of the connection between ground stations and satellites, caused by both the satellite’s orbital movement and fluctuating atmospheric attenuation. Thus, it is necessary to design novel schemes to dynamically allocate resources for satellite QKD networks that adapt to evolving network conditions in different time intervals. In this work, we investigate the problem of resource allocation in satellite QKD networks taking into account the changing key generation rates, calculated according to evolving weather conditions and satellite visibility. We first model the achievable key rate of connections between satellite and ground stations under different weather conditions, which is used as an input for optimization. We formulate a Mixed-Integer Linear Programming (MILP) model to allocate resources in satellite QKD networks, which decides both link assignments (i.e., deciding which ground to connect to for satellites) and the appropriate routing path for the trusted relay. In addition, the MILP models multiple timeslots and considers keys stored in the quantum key pool (QKP), allowing keys generated during low-load periods to be used later during high-load periods. Moreover, we propose to decide the link configuration with heuristic algorithms and then utilize ILP to decide the appropriate routing path for the trusted relay, which significantly reduces the execution time. The numerical results show that incorporating link configuration within the ILP achieves up to 20% more total served keys compared to heuristicbased baseline approaches, but with an execution time up to 700x longer.
The growing integration of power grids with communication networks underscores the critical importance of cybersecurity. Quantum key distribution (QKD) offers a potent approach to secure power information based on physics laws. However, the challenge of limited quantum keys due to low key rates remains unresolved, necessitating the optimal planning of QKD networks. Therefore, this paper proposes a QKD network planning method to address uncertainties in power communication. First, the fiber QKD-based communication network is introduced. Then, the QKD network planning problem is formulated as a two-stage stochastic mixed-integer linear programming (MILP) model. The first stage models the quantum device deployment considering QKD processes and investment budgets. The second stage takes demand response as an example, considering scenario-dependent communication requests that fluctuate with the output of renewable energy resources. Finally, the proposed method is validated by a modified IEEE 30-bus system, with numerical results verifying its effectiveness in improving power cybersecurity.
With the advent of interconnected quantum computers, i.e., distributed quantum computing (DQC), multiple quantum computers can now collaborate via quantum networks to perform massively complex computational tasks. However, DQC faces problems sharing quantum information because it cannot be cloned or duplicated between quantum computers. Thanks to advanced quantum mechanics, quantum computers can teleport quantum information across quantum networks. However, challenges to utilizing efficiently quantum resources, e.g., quantum computers and quantum channels, arise in DQC due to their capabilities and properties, such as uncertain qubit fidelity and quantum channel noise. In this paper, we propose a resource allocation scheme for DQC based on stochastic programming to minimize the total deployment cost for quantum resources. Essentially, the two-stage stochastic programming model is formulated to handle the uncertainty of quantum computing demands, computing power, and fidelity in quantum networks. The performance evaluation demonstrates the effectiveness and ability of the proposed scheme to balance the utilization of quantum computers and on-demand quantum computers while minimizing the overall cost of provisioning under uncertainty.
The increasing focus on privacy and security in 6G networks, which are intelligence-native, necessitates the use of quantum key distribution-secured semantic information communication (QKD-SIC) to protect confidential data. In QKD-SIC systems, edge devices connected via quantum channels can efficiently encrypt semantic information from the semantic source, and securely transmit the encrypted semantic information to the semantic destination. In this article, we consider an efficient resource (i.e., quantum key distribution (QKD) and KM wavelengths) sharing problem to support QKD-SIC systems under the uncertainty of semantic information generated by edge devices. In such a system, QKD service providers offer QKD services with different subscription options to the edge devices. The QKD services are envisioned to follow cloud computing that has the subscription in the reservation and on-demand options, i.e., for long and short (immediate) terms, respectively. As such, to reduce the cost for the edge device users, we propose a QKD resource management framework for the edge devices communicating semantic information. The framework is based on a two-stage stochastic optimization model to achieve optimal QKD deployment. Moreover, to reduce the deployment cost of QKD service providers, QKD resources in the proposed framework can be utilized based on efficient QKD-SIC resource management, including semantic information transmission among edge devices, secret-key provisioning, and cooperation formation among QKD service providers. In detail, the formulated two-stage stochastic optimization model can achieve the optimal QKD-SIC resource deployment while meeting the secret-key requirements for semantic information transmission of edge devices. Moreover, to share the cost of the QKD resource pool among cooperative QKD service providers forming a coalition in a fair and interpretable manner, the proposed framework leverages the concept of Shapley value from cooperative game theory as a solution. Experimental results demonstrate that the proposed framework can reduce the deployment cost by about 40% compared with existing noncooperative baselines.