With the advancement of quantum computing, the security of public key cryptography is under serious threat. To guarantee security in the quantum era, Quantum Key Distribution has become a competitive solution. QKD networks can be classified into measurement-device-dependent network and measurement-device-independent network. In measurement-device-dependent networks, the information is available for all trusted relays. This means that all trusted relays are strongly trusted relays that require strict control, which is difficult to realize. To address this issue, measurement-device-independent networks reduce the proportion of strongly trusted relay nodes by introducing untrusted relays. However, due to the higher key rate of measurement-device-dependent protocols over short distances, the communication capability of measurement-device-independent networks has a degradation compared to measurement-device-dependent networks. Therefore, how to reduce the dependence of QKD networks on strong trusted relays without significantly affecting the communication capability has become a major issue in the practicalization process of QKD networks. To address this issue, a novel Multi-Protocol Collaborative networking cell is proposed in this paper. The QKD network built by the MPC networking cell reduces the dependence on strongly trusted relays by combining the two protocols to introduce weak trusted relays while maintaining the high communication capacity. What's more, to further enhance the overall performance of the QKD network, an optimal topology design method is presented via the proposed flow-based mathematical model and optimization method. The simulation results show that the proposed scheme reduces the dependence on strongly trusted relays without a significant reduction in communication capability, our work holds great significance in promoting the practicalization of QKD networks.
With the advancement of quantum computing, the security of public key cryptography is under serious threat. To guarantee security in the quantum era, Quantum Key Distribution has become a competitive solution. QKD networks can be classified into measurement-device-dependent network and measurement-device-independent network. In measurement-device-dependent networks, the information is available for all trusted relays. This means that all trusted relays are strongly trusted relays that require strict control, which is difficult to realize. To address this issue, measurement-device-independent networks reduce the proportion of strongly trusted relay nodes by introducing untrusted relays. However, due to the higher key rate of measurement-device-dependent protocols over short distances, the communication capability of measurement-device-independent networks has a degradation compared to measurement-device-dependent networks. Therefore, how to reduce the dependence of QKD networks on strong trusted relays without significantly affecting the communication capability has become a major issue in the practicalization process of QKD networks. To address this issue, a novel Multi-Protocol Collaborative networking cell is proposed in this paper. The QKD network built by the MPC networking cell reduces the dependence on strongly trusted relays by combining the two protocols to introduce weak trusted relays while maintaining the high communication capacity. What's more, to further enhance the overall performance of the QKD network, an optimal topology design method is presented via the proposed flow-based mathematical model and optimization method. The simulation results show that the proposed scheme reduces the dependence on strongly trusted relays without a significant reduction in communication capability, our work holds great significance in promoting the practicalization of QKD networks.
The development of emerging consumer technologies such as the Internet of Things (IoT), artificial intelligence (AI), and cloud computing brings convenience but also raises critical concerns about securing communication data. Quantum computing threatens the security of classical public key cryptography, making post-quantum data protection essential. Quantum Key Distribution (QKD) networks offer a solution, but the dependence on trusted relays raises security concerns. The existing QKD networks mainly consist of two types: measurement-device-dependent protocol based QKD networks which have a high dependence on trusted relays, and measurement-device-independent protocol based QKD networks which have a weak dependence on trusted relays but communication capability is limited. This paper proposes a Multi-Protocol Collaborative (MPC) networking cell combining both types of QKD protocol, which can reduce the dependence on trusted relays while maintaining a high communication capacity, and consequently has an enhanced practicality. An optimal topology method is also designed to further enhance the performance of the networks. Results show that communication capacity is improved 37 times compared to measurement-device-independent protocol based QKD networks. In addition, 23% reduction in the dependence on trusted relays compared to measurement-device-dependent protocol based QKD networks. By overcoming the trade-off between trust and capacity, this work significantly advances the practicalization of QKD networks in consumer electronics.
Quantum Key Distribution (QKD) is a promising technology that provides proven unconditional security based on fundamentals of quantum physics, especially for point-to-point communications. It could be applied in large-scale optical networks for long-distance key provisioning mainly by three relaying methods: quantum-repeater-based QKD, trusted-relay-based QKD, and measurement-device-independent QKD (MDI-QKD). However, quantum-repeater-based QKD is still under study because of the immature technologies such as the preliminary quantum memory. The trusted-relay-based QKD is vulnerable since insecurity of non-ideal single-photon sources and detectors cannot be ignored in practical applications. On the other hand, for MDI-QKD, there exists a limitation on its key rate under long-distance communications. According to these limitations, embedding protocols like MDI-QKD into the existing trusted-relay-based QKD secured optical networks (QKD-ON) with usage of untrusted relays is a promising key-provisioning scheme. In this paper, we study such partially-trusted relay scenarios and focus on its routing of keys in different kinds of typical network topologies. A partially-trusted-relay-based QKD method is described, which can allow a pair of optical nodes sharing secret keys under the coexistence of trusted relays and untrusted relays. The secret-key provisioning with collaborative routing (SKP-CR) algorithm is proposed to search for the optimal key-relay routing path. We perform the simulations with different proportion of trusted relays versus untrusted relays, initial secret keys in the quantum key pools (QKPs), and traffic load. The simulations verify that theSKP-CRalgorithm can significantly outperform the conventional trusted-relay-based scheme in terms of key-distribution success rate with an improvement of up to62%with a mesh topology.
Quantum key distribution (QKD) can serve large numbers of users with unconditional secure communication, in which measurement-device-independent (MDI) QKD protocol can conveniently enhance realistic security by eliminating all detector side channels. In multi-user scenarios, MDI-QKD networks should meet the requirements of reliability and robustness. Around the issues, we complete a series of work on performance improvement, low-cost deployment, and robust networking. First is to answer how to change the trusted node to the untrusted node with low cost, here we propose and demonstrate an MDIQKD which is compatible with phase encoding BB84 networks, allowing for economical deployment of MDI-QKD networks and reconciliation between high key rate and high realistic security in the same network. Then we make the MDI networks more robust. We design an MDI-QKD networking scheme for multi-user access where more than two users can generate keys synchronously regardless of aligning reference frames and compensating channel disturbance on polarization. Third, we find a general method to distil secure keys from quantum discord, which is different to the previous entanglement-based frameworks of MDI-QKD, allowing imperfect preparation and measurement of quantum states. The series of work can help the practical application of MDI-QKD networks, and promote the development of quantum networks.
Abstract As the first stage of the quantum Internet, quantum key distribution (QKD) networks hold the promise of providing long-term security for diverse users. Most existing QKD networks have been constructed based on independent QKD protocols, and they commonly rely on the deployment of single-protocol trusted relay chains for long reach. Driven by the evolution of QKD protocols, large-scale QKD networking is expected to migrate from a single-protocol to a multi-protocol paradigm, during which some useful evolutionary elements for the later stages of the quantum Internet may be incorporated. In this work, we delve into a pivotal technique for large-scale QKD networking, namely, multi-protocol relay chaining. A multi-protocol relay chain is established by connecting a set of trusted/untrusted relays relying on multiple QKD protocols between a pair of QKD nodes. The structures of diverse multi-protocol relay chains are described, based on which the associated model is formulated and the policies are defined for the deployment of multi-protocol relay chains. Furthermore, we propose three multi-protocol relay chaining heuristics. Numerical simulations indicate that the designed heuristics can effectively reduce the number of trusted relays deployed and enhance the average security level versus the commonly used single-protocol trusted relay chaining methods on backbone network topologies.
Quantum Key Distribution (QKD) has demonstrated unique and significant advantages in secure communication. In particular, Measurement-Device-Independent QKD (MDI-QKD), which is independent of measurement devices, increases data transmission distances and addresses the issue of low security in trusted relays. Therefore, in this work, we investigate QKD networks based on trusted and untrusted relays over optical backbone networks, providing a cost-optimal solution for the deployment and implementation of QKD networks. Specifically, this paper describes the QKD network and defines a new cost model, which not only fully considers the diverse impact factors of deployment costs but also meets the requirements for sharing network elements in response to different QKD chain requests. Based on cost model, this paper further proposes a cost-optimal heuristic algorithm for hybrid QKD network deployment, which can provide an economical and secure deployment solution for QKD networks. Extensive simulation experiments are conducted and the experimental results show that the proposed method outperforms current mainstream QKD network deployment algorithms in both deployment cost and security. Moreover, as the network scale increases, the advantages of our algorithm become more pronounced. Compared to mainstream algorithms, our method achieve an improvement of 17.7% -64.3% in cost savings and 1.19 to 3.24 times in security levels.
The development of quantum networks will be paramount towards practical and secure telecommunications. These networks will need to sign and distribute information between many parties with information-theoretic security, requiring both quantum digital signatures (QDS) and quantum key distribution (QKD). Here, we introduce and experimentally realise a quantum network architecture, where the nodes are fully connected using a minimum amount of physical links. The central node of the network can act either as a totally untrusted relay, connecting the end users via the recently introduced measurement-device-independent (MDI)-QKD, or as a trusted recipient directly communicating with the end users via QKD. Using this network, we perform a proof-of-principle demonstration of QDS mediated by MDI-QKD. For that, we devised an efficient protocol to distil multiple signatures from the same block of data, thus reducing the statistical fluctuations in the sample and greatly enhancing the final QDS rate in the finite-size scenario.