We show the security of multi-user key establishment on a single line of quantum communication. More precisely, we consider a quantum communication architecture where the qubit generation and measurement happen at the two ends of the line, whilst intermediate parties are limited to single-qubit unitary transforms. This network topology has been previously introduced to implement quantum-assisted secret-sharing protocols for classical data, as well as the key establishment, and secure computing. This architecture has numerous advantages. The intermediate nodes are only using simplified hardware, which makes them easier to implement. Moreover, key establishment between arbitrary pairs of parties in the network does not require key routing through intermediate nodes. This is in contrast with quantum key distribution (QKD) networks for which non-adjacent nodes need intermediate ones to route keys, thereby revealing these keys to intermediate parties and consuming previously established ones to secure the routing process. Our main result is to show the security of key establishment on quantum line networks. We show the security using the framework of abstract cryptography. This immediately makes the security composable, showing that the keys can be used for encryption or other tasks.We show the security of multi-user key establishment on a single line of quantum communication. More precisely, we consider a quantum communication architecture where the qubit generation and measurement happen at the two ends of the line, whilst intermediate parties are limited to single-qubit unitary transforms. This network topology has been previously introduced to implement quantum-assisted secret-sharing protocols for classical data, as well as the key establishment, and secure computing. This architecture has numerous advantages. The intermediate nodes are only using simplified hardware, which makes them easier to implement. Moreover, key establishment between arbitrary pairs of parties in the network does not require key routing through intermediate nodes. This is in contrast with quantum key distribution (QKD) networks for which non-adjacent nodes need intermediate ones to route keys, thereby revealing these keys to intermediate parties and consuming previously established ones to secure the routing process. Our main result is to show the security of key establishment on quantum line networks. We show the security using the framework of abstract cryptography. This immediately makes the security composable, showing that the keys can be used for encryption or other tasks.

International Conference on Quantum Communications, Networking, and Computing (QCNC)Jul 1, 20248 citations

Security of a Secret Sharing Protocol on the Qline

Alex B. Grilo, Lucas Hanouz, Anne Marin

Secret sharing is a fundamental primitive in cryptography, and it can be achieved even with perfect security. However, the distribution of shares requires computational assumptions, which can compromise the overall security of the protocol. While traditional Quantum Key Distribution (QKD) can maintain security, its widespread deployment in general networks would incur prohibitive costs. In this work, we present a quantum protocol for distributing additive secret sharing of 0, which we prove to be composably secure within the Abstract Cryptography framework. Moreover, our protocol targets the Qline, a recently proposed quantum network architecture designed to simplify and reduce the cost of quantum communication. Once the shares are distributed, they can be used to securely perform a wide range of cryptographic tasks, including standard additive secret sharing, anonymous veto, and symmetric key establishment.Secret sharing is a fundamental primitive in cryptography, and it can be achieved even with perfect security. However, the distribution of shares requires computational assumptions, which can compromise the overall security of the protocol. While traditional Quantum Key Distribution (QKD) can maintain security, its widespread deployment in general networks would incur prohibitive costs. In this work, we present a quantum protocol for distributing additive secret sharing of 0, which we prove to be composably secure within the Abstract Cryptography framework. Moreover, our protocol targets the Qline, a recently proposed quantum network architecture designed to simplify and reduce the cost of quantum communication. Once the shares are distributed, they can be used to securely perform a wide range of cryptographic tasks, including standard additive secret sharing, anonymous veto, and symmetric key establishment.

arXiv:2504.19702International Conference on Quantum Communications, Networking, and Computing (QCNC)Apr 6, 20260 citations

Scalable Authenticated Group Key Establishment in Quantum and Post-Quantum Networks

María Isabel González Vasco, Rainer Steinwandt

Establishing secure keys over untrusted networks is one of the most fundamental cryptographic tasks. While two-party key establishment protocols are available for many scenarios, even offering resistance to potential adversaries equipped with quantum computing resources, the multi-party scenario is not as well understood. In particular, there is a need to find designs that can make the most of the technologies available to each party involved in a cooperative n-party key establishment. We propose an authenticated key establishment protocol involving $n\geqslant 2$ parties, assuming that some—possibly all—network nodes have the potential to implement quantum key distribution (in pairs), while others only have access to standard technology. The protocol allows for the cooperative construction of a shared secret key from partial keys established by quantum and post-quantum solutions, which in turn can be implemented by different building blocks. We give a formal security analysis of our proposal using a hybrid security model simultaneously capturing quantum and classical actions and capabilities.Establishing secure keys over untrusted networks is one of the most fundamental cryptographic tasks. While two-party key establishment protocols are available for many scenarios, even offering resistance to potential adversaries equipped with quantum computing resources, the multi-party scenario is not as well understood. In particular, there is a need to find designs that can make the most of the technologies available to each party involved in a cooperative n-party key establishment. We propose an authenticated key establishment protocol involving $n\geqslant 2$ parties, assuming that some—possibly all—network nodes have the potential to implement quantum key distribution (in pairs), while others only have access to standard technology. The protocol allows for the cooperative construction of a shared secret key from partial keys established by quantum and post-quantum solutions, which in turn can be implemented by different building blocks. We give a formal security analysis of our proposal using a hybrid security model simultaneously capturing quantum and classical actions and capabilities.

InformaticaJan 1, 20252 citations

Quantum cryptography on multi-user network architectures

Patrick D. Kumavor, Alan C. Beal, Susanne F. Yelin +2 more

Quantum cryptography applies the uncertainty principle and the no-cloning theorem to allow to parties to share a secret key over an ultra-secure link. Present quantum cryptography technologies provide encryption key distribution only between two users. However, practical implementations of encryption key distribution schemes require establishing secure quantum communications amongst multiple users. This paper looks at some of the advantages and drawbacks of some common network topologies that could be used in sending cryptographic keys across a network consisting of multiple users. These topologies are the star, ring, and bus networks. Their performances are compared and analyzed using quantum bit error rate analysis. The paper also presents an experimental demonstration of a six-user quantum key distribution network implemented on a bus topology.Quantum cryptography applies the uncertainty principle and the no-cloning theorem to allow to parties to share a secret key over an ultra-secure link. Present quantum cryptography technologies provide encryption key distribution only between two users. However, practical implementations of encryption key distribution schemes require establishing secure quantum communications amongst multiple users. This paper looks at some of the advantages and drawbacks of some common network topologies that could be used in sending cryptographic keys across a network consisting of multiple users. These topologies are the star, ring, and bus networks. Their performances are compared and analyzed using quantum bit error rate analysis. The paper also presents an experimental demonstration of a six-user quantum key distribution network implemented on a bus topology.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEMay 5, 20061 citation

Approaches to Developing Key Distribution Protocols Based on Quantum Key Distribution

Yenlik Begimbayeva

Quantum protocols for generating shared secret keys represent an effective method of ensuring secure information transmission using quantum communication channels. However, they are limited in scalability due to the physical constraints of quantum channels, which necessitates the use of classical communication channels for exchanging information between participants. This leads to the necessity of developing security threat models and network protection, especially in the case of hybrid networks, where quantum channels are used alongside classical ones. The peculiarity of constructing quantum key distribution protocols is associated with the costliness of implementation and implies the inevitable use of classical communication channels for key distribution. This paper addresses the task of ensuring the security of communication between subscribers not directly connected by quantum channels, through intermediary nodes, and analyzes threats from internal and external adversaries. Special attention is paid to situations where both types of adversaries have information about the processes and protocols in the network. The paper examines widely used key distribution protocols employed in practice. It describes the main security requirements applied to key distribution protocols, and presents the results of an analysis of the compliance of the discussed protocols with these requirementsQuantum protocols for generating shared secret keys represent an effective method of ensuring secure information transmission using quantum communication channels. However, they are limited in scalability due to the physical constraints of quantum channels, which necessitates the use of classical communication channels for exchanging information between participants. This leads to the necessity of developing security threat models and network protection, especially in the case of hybrid networks, where quantum channels are used alongside classical ones. The peculiarity of constructing quantum key distribution protocols is associated with the costliness of implementation and implies the inevitable use of classical communication channels for key distribution. This paper addresses the task of ensuring the security of communication between subscribers not directly connected by quantum channels, through intermediary nodes, and analyzes threats from internal and external adversaries. Special attention is paid to situations where both types of adversaries have information about the processes and protocols in the network. The paper examines widely used key distribution protocols employed in practice. It describes the main security requirements applied to key distribution protocols, and presents the results of an analysis of the compliance of the discussed protocols with these requirements

Journal of Electrical SystemsMay 4, 20240 citations

Quantum Relay Nodes: Enhancing Security and Scalability in Quantum Key Distribution Networks

Abhijit Dey, Sujit Biswas, Saikat Bose +1 more

Quantum Key Distribution (QKD) has emerged as a promising technology for secure the communication because its security is achieved through the physical laws of quantum mechanics, rather than being based on mathematical problems. In most of the earlier implementations, QKD relied on the direct exchange of the secret keys between two users. Once implemented in a practical system outside of a controlled laboratory setting, QKD experiences complications associated with the limited distances, communication losses, and vulnerabilities to eavesdropping in the multi-user network configurations, compromising its ability to be this third-generation secure communication system. In this work, we show how quantum relay nodes can be implemented as points along a QKD network. The relay nodes provide additional advantages such as extending the communication distances, increasing eavesdropping resistance and allowing for more sophisticated configurations. While relying on theoretical models and experimentally motivated studies, this paper discusses advantages of implementing a relay architecture into a QKD network and highlights technical difficulties that need to be addressed prior to widespread implementation.Quantum Key Distribution (QKD) has emerged as a promising technology for secure the communication because its security is achieved through the physical laws of quantum mechanics, rather than being based on mathematical problems. In most of the earlier implementations, QKD relied on the direct exchange of the secret keys between two users. Once implemented in a practical system outside of a controlled laboratory setting, QKD experiences complications associated with the limited distances, communication losses, and vulnerabilities to eavesdropping in the multi-user network configurations, compromising its ability to be this third-generation secure communication system. In this work, we show how quantum relay nodes can be implemented as points along a QKD network. The relay nodes provide additional advantages such as extending the communication distances, increasing eavesdropping resistance and allowing for more sophisticated configurations. While relying on theoretical models and experimentally motivated studies, this paper discusses advantages of implementing a relay architecture into a QKD network and highlights technical difficulties that need to be addressed prior to widespread implementation.

CRC Press eBooksSep 3, 20260 citations

n\geqslant 2

parties, assuming that some—possibly all—network nodes have the potential to implement quantum key distribution (in pairs), while others only have access to standard technology. The protocol allows for the cooperative construction of a shared secret key from partial keys established by quantum and post-quantum solutions, which in turn can be implemented by different building blocks. We give a formal security analysis of our proposal using a hybrid security model simultaneously capturing quantum and classical actions and capabilities.