Scalable Authentication and Optimal Flooding in a Quantum Network
Naomi R. Solomons, Alasdair I. Fletcher, Djeylan Aktas, Natarajan Venkatachalam, Sören Wengerowsky, Martin Lončarić, Sebastian Philipp Neumann, Bo Liu, Željko Samec, Mario Stipčević, Rupert Ursin, Stefano Pirandola, John Rarity, Siddarth Koduru Joshi
The global interest in quantum networks stems from the security guaranteed by the laws of physics.The deployment of quantum networks means facing the challenges of scaling up the physical hardware and, more importantly, of scaling up all other network layers and optimally utilizing network resources.Here, we consider two related protocols and their experimental demonstrations on an eight-user quantum network test bed, and discuss their usefulness with the aid of example use cases.First, we consider an authentication-transfer protocol to manage a fundamental limitation of quantum communication-the need for a preshared key between every pair of users linked together on the quantum network.By temporarily trusting some intermediary nodes for a short period of time (< 35 min in our network), we can generate and distribute these initial authentication keys with a very high level of security.Second, when end users quantify their trust in intermediary nodes, our flooding protocol can be used to improve both end-to-end communication speeds and increase security against malicious nodes.
The global interest in quantum networks stems from the security guaranteed by the laws of physics.The deployment of quantum networks means facing the challenges of scaling up the physical hardware and, more importantly, of scaling up all other network layers and optimally utilizing network resources.Here, we consider two related protocols and their experimental demonstrations on an eight-user quantum network test bed, and discuss their usefulness with the aid of example use cases.First, we consider an authentication-transfer protocol to manage a fundamental limitation of quantum communication-the need for a preshared key between every pair of users linked together on the quantum network.By temporarily trusting some intermediary nodes for a short period of time (< 35 min in our network), we can generate and distribute these initial authentication keys with a very high level of security.Second, when end users quantify their trust in intermediary nodes, our flooding protocol can be used to improve both end-to-end communication speeds and increase security against malicious nodes.
Quantum key distribution allows secure key distribution between remote communication parties. In a quantum network, multiple users are connected by quantum links for key distribution and classical links for encrypted data transmission. When the quantum network structure becomes complicated with a large number of users, it is important to investigate network issues, including security, key management, latency, reliability, scalability, and cost. In this work, we utilize the classical network theory and graph theory to establish a framework for a quantum network, addressing two critical issues, security and key management. First, we design a communication scheme with the highest security level that trusts a minimum number of intermediate nodes. Second, when the quantum key is a limited resource, we design key management and data scheduling schemes to optimize the utility of data transmission. Our results can be directly applied to the current metropolitan and free-space quantum network implementations and can potentially be a standard approach for future quantum network designs.
As an extension of quantum key distribution, secure communication among multiple users is a basic task in a quantum network. When the quantum network structure becomes complicated with a large number of users, it is important to investigate network issues, including security, key management, latency, reliability, scalability, and cost. In this work, we utilize the classical network theory and graph theory to address two critical issues in a quantum network, security and key management. First, we design a communication scheme with the highest security level that trusts a minimum number of intermediate nodes. Second, when the quantum key is a limited resource, we design key management and data scheduling schemes to optimize the utility of data transmission. Our results can be directly applied to the current metropolitan and free-space quantum network implementations and can potentially be a standard approach for future quantum network designs.
Quantum communication is rapidly gaining popularity due to its high security and technological maturity. However, most implementations are limited to just two communicating parties (users). Quantum communication networks aim to connect a multitude of users. Here, we present a fully connected quantum communication network on a city-wide scale without active switching or trusted nodes. We demonstrate simultaneous and secure connections between all 28 pairings of eight users. Our novel network topology is easily scalable to many users, allows traffic management features, and minimizes the infrastructure as well as the user hardware needed.
Besides true quantum repeaters, a trusted node paradigm seems to be inevitable for practical implementations (at least in the short term), and one should consider configurations of trusted nodes as the basis for global quantum networks. In this paper, we estimate how the introduction of additional connections between trusted nodes through one, two, etc., nodes (i.e., connection density) to a quantum network with serial connections of trusted nodes affects its security. We provide proper scaling of the failure probability of authentication and quantum key distribution protocols to the level of the whole quantum network. Expressions of the failure probability dependent on the total number of connected nodes between users and the connection density for the given mean failure probability of each element are derived. The result provides an explicit trade-off between an increase of key transport security and a consequent increase of spent resources. We believe that the obtained result may be useful for both the design of future networks and optimization of existing ones.
In this review, we survey the cryptographic task of authentication from the perspective of quantum communication. We review three main flavours of authentication that are often conflated in the literature: authentication of classical messages, authentication of quantum messages, and entity authentication, also covering recent hardware-assisted approaches. We compare representative protocols for each functionality in terms of their security assumptions, set-up requirements, composability, and scalability in large or dynamic networks, and use these criteria to identify and recommend suitable candidates. Finally, applications are surveyed: we provide a detailed case study of authentication and quantum key distribution (QKD), then extend the discussion to protocols beyond QKD, where the role of authentication is more complex. Our take-home message is that an authentication requirement is not an intrinsic limitation of quantum networks: as with all secure communication, each protocol relies on a particular authentication resource, and the security claim of that protocol is meaningful only once the authentication resource and its deployment assumptions are made explicit. At the same time, the existing classical and quantum literature already offers a range of quantum-secure authentication schemes, which can support different applications when carefully matched to the required functionality, assumptions, and security guarantees.