Quantum key distribution (QKD) is currently the only visible technology for secure symmetric key exchange between communicating parties. However, existing quantum photon sources (PSs) in QKD networks for generating keys between nodes are costly but offer limited achievable key rates. Moreover, achievable key rates across links diminish drastically with link distance, underscoring the importance of effectively identifying relay paths and strategically allocating PS resources. To optimize network costs, it is essential to jointly deploy PSs, allocate key rates across links, and determine relay paths based on anticipated traffic. To this end, we formulate a novel optimization problem, termed DAP, which simultaneously considers PS placement, key rate allocation, and relay path identification. Our proposed$O(\log\vert V\vert)$approximation algorithm, ADAP, leverages an advanced linear programming (LP) conversion with tailored rounding techniques. Simulation results manifest that ADAP achieves at least an 83 % reduction in the number of PSs.
Quantum key distribution (QKD) is currently the only visible technology for secure symmetric key exchange between communicating parties. However, existing quantum photon sources (PSs) in QKD networks for generating keys between nodes are costly but offer limited achievable key rates. Moreover, achievable key rates across links diminish drastically with link distance, underscoring the importance of effectively identifying relay paths and strategically allocating PS resources. To optimize network costs, it is essential to jointly deploy PSs, allocate key rates across links, and determine relay paths based on anticipated traffic. To this end, we formulate a novel optimization problem, termed DAP, which simultaneously considers PS placement, key rate allocation, and relay path identification. Our proposedO(log∣V∣)approximation algorithm, ADAP, leverages an advanced linear programming (LP) conversion with tailored rounding techniques. Simulation results manifest that ADAP achieves at least an 83 % reduction in the number of PSs.
Quantum Key Distribution (QKD) is considered to be an ultimate solution to communication security. However, current QKD devices, especially quantum photon sources, are expensive, and they can generate secret keys only at a low rate. In this paper, we design a system named RPSP for trusted relay-based QKD networks to not only minimize the number of photon sources needed in a network to ensure at least one feasible relay path exists for any potential QKD requests but also save the time to complete a batch of end-to-end QKD requests by jointly optimizing the routing of relay paths and the provisioning of photon sources along each relay path. Compared with existing works, RPSP focuses on a more practical scenario where only some of the nodes are equipped with photon sources and it leverages optical switching to enable dynamic photon source provisioning such that we can utilize such QKD devices in a more efficient way. Extensive simulations show that compared with baseline schemes, RPSP can save up to 87% of the photon sources needed in a trusted relay based QKD network, and 36% of the time to complete a batch of QKD requests.
Quantum Key Distribution (QKD) is a recent technology for secure distribution of symmetric keys, which is currently being deployed to increase communications security against quantum attacks. However, the key rate achievable over a weak quantum signal is limited by the link performance (e.g., loss and noise) and propagation distance, especially in multi-node QKD networks, making it necessary to design a scheme to efficiently and timely distribute keys to the various nodes. In this work, we formulate, using a Mixed Integer Linear Programming (MILP) model, a novel Routing, Channel, and Key-rate Assignment (RCKA) problem for QKD with Quantum Key Pool (QKP), which exploits the opportunity of using trusted relays and optical bypass. Our formulation accounts for the possibility to build a quantum key distribution path that combines both quantum channels and trusted relays to increase the acceptance ratio of key rate requests. Leveraging different versions of the proposed MILP model, we evaluate several strategies exploiting different combinations of trusted relays and optical bypass for the RCKA problem. Results show how different trade-offs between security and resource-efficiency (expressed in terms of acceptance ratio of key rate requests vs. key storing rate in QKP) can be achieved when adopting trusted-relay and/or optical-bypass technologies. Trusted relays can provide a higher acceptance ratio when the number of QKD modules (transmitters or receivers) is sufficiently large, while optical bypass, which does not require the implementation of expensive trusted relays, is preferable when the number of QKD modules is a limiting factor.
There is a need to ensure unconditionally secure communications between different sites of an organization. We use quantum key distribution (QKD) protocol to provide a continuous stream of secret key bits to each communicating pair for message encryption through one-time-pad (OTP) cryptography. Due to long distance between different sites, trusted nodes are used to relay each service key in a hop-by-hop manner from one end node to another end node of a communicating pair. In a QKD network, routes for key relaying can be affected by availability of relay key bits at trusted nodes. Also, relay key allocation among different routes can impact security. We consider the scenario of supporting multiple communicating pairs, where each pair demands delivery of a certain service key rate across the QKD network, and trusted nodes may not have sufficient relay key rates to perform bitwise encryption to protect the service key. Hence, there is a need to allocate the limited relay key bits to meet all service key delivery demands while considering its effects on security. We propose to perform jointly routing and relay key allocation to minimize attack success probability. We have formulated the joint problem as an optimization and further proposed an efficient algorithm to find the optimal solutions. We have evaluated the proposed algorithm to confirm its ability and efficiency in finding optimal routes and relay key allocations. For the specific network topology that we have adopted, results show that the minimum number of required trusted nodes increases linearly when end nodes are added to the system. Furthermore, we can achieve a higher security level by adding more trusted nodes in a QKD network. But increasing the number of trusted nodes beyond the minimum requirement may not continue to reduce significantly the attack success probability.
Quantum Key Distribution (QKD) is considered to be the ultimate solution to communication security. However, current QKD devices, especially quantum photon sources, are expensive, and they can generate secret keys only at a low rate. In this paper, we first consider homogeneous trusted-relay-based QKD networks where every request has the same amount of secret key requirement and every photon source has the same key distribution rate, and design an approach named RPSP to not only minimize the number of photon sources needed in a network to ensure at least one feasible relay path exists for any potential QKD requests but also save the time to complete a batch of QKD requests by jointly optimizing the routing of relay paths and the provisioning of photon sources to distribute secret keys. Then, we extend RPSP to RPSP-HN which can be applied to heterogeneous networks where requests have different secret key requirements and photon sources distribute keys at different rates. Furthermore, we also extend RPSP to RPSP-HY, which considers that some of the nodes in a network is untrusted. Compared with existing works, RPSP and its extensions focus on more practical scenarios where only some of the nodes are equipped with photon sources and they leverage optical switching to enable dynamic photon source provisioning such that we can utilize QKD devices more efficiently. Extensive simulations show that compared with baseline schemes, RPSP, RPSP-HN, and RPSP-HY can save up to 33%, 37%, and 25% of the time to complete a batch of QKD requests in homogeneous, heterogeneous, and hybrid QKD networks, respectively.
Quantum Key Distribution (QKD) is currently being explored as a solution to the threats posed to current cryptographic protocols by the evolution of quantum computers and algorithms. However, single-photon quantum signals used for QKD permit to achieve key rates strongly limited by link performance (e.g., loss and noise) and propagation distance, especially in multi-node QKD networks, making it necessary to design a scheme to efficiently and timely distribute keys to the various nodes. In this work, we introduce the new problem of joint Routing, Channel, Key-rate and Time-slot Assignment (RCKTA), which is addressed with four different network settings, i.e., allowing or not the use of optical bypass (OB) and trusted relay (TR). We first prove the NP-hardness of the RCKTA problem for all network settings and formulate it using a Mixed Integer Linear Programming (MILP) model that combines both quantum channels and quantum key pool (QKP) to provide an optimized solution in terms of number of accepted key rate requests and key storing rate. To deal with problem complexity, we also propose a heuristic algorithm based on an auxiliary graph, and show that it is able to obtain near-optimal solutions in polynomial time. Results show that allowing OB and TR achieves an acceptance ratio of 39% and 14% higher than that of OB and TR, respectively. Remarkably, these acceptance ratios are obtained with up to 46% less QKD modules (transceivers) compared to TR and only few (less than 1 per path) additional QKD modules than OB.
Quantum secure communication networks based on quantum key distribution (QKD) technology are gradually improving, which can provide remote and networked key services for multiple users. This paper proposes a key distribution solution for latency and resource optimization in trusted relay QKD networks. In this scheme, the key distribution process between trusted relay nodes is presented as a joint optimization problem by considering the constraints of service delay, bandwidth, path resource consumption, quality loss and remaining quantum key quantity. In this paper, we treat key distribution as a bi-objective minimization problem, maintaining a trade-off between service delay and path resource consumption. Specifically, we propose a dynamic key distribution framework based on linear programming and particle swarm optimization. Simulation results show that the key distribution path selection in this scheme can be adjusted according to the service delay, key quality, and path resource consumption. Compared with the Random and customized OSPF policies, this scheme has higher performance. More specifically, the solution reduced average service latency by 27% while reducing path resource consumption by 560%.