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arXiv:2103.08722 · New Journal of Physics

Anonymous and secret communication in quantum networks

Christopher Thalacker, Frederik Hahn, Jarn de Jong, Anna Pappa, Stefanie Barz

Published Jul 27, 2021• 29 citations
arXivHTMLPDF

Abstract

Abstract Secure communication is one of the key applications of quantum networks. In recent years, following the demands for identity protection in classical communication protocols, the need for anonymity has also emerged for quantum networks. Here, we demonstrate that quantum physics allows parties—besides communicating securely over a network—to also keep their identities secret. We implement such an anonymous quantum conference key agreement by sharing multipartite entangled states in a quantum network. We demonstrate the protocol with four parties and establish keys in subsets of the network—different combinations of two and three parties—whilst keeping the participating parties anonymous. We additionally show that the protocol is verifiable and run multiple key generation and verification routines. Our work thus addresses one of the key challenges of networked communication: keeping the identities of the communicating parties private.

DOI
10.1088/1367-2630/ac1808

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Abstract Secure communication is one of the key applications of quantum networks. In recent years, following the demands for identity protection in classical communication protocols, the need for anonymity has also emerged for quantum networks. Here, we demonstrate that quantum physics allows parties—besides communicating securely over a network—to also keep their identities secret. We implement such an anonymous quantum conference key agreement by sharing multipartite entangled states in a quantum network. We demonstrate the protocol with four parties and establish keys in subsets of the network—different combinations of two and three parties—whilst keeping the participating parties anonymous. We additionally show that the protocol is verifiable and run multiple key generation and verification routines. Our work thus addresses one of the key challenges of networked communication: keeping the identities of the communicating parties private.
Sharing multi-partite quantum entanglement between parties allows for diverse secure communication tasks to be performed. Among them, conference key agreement (CKA), an extension of key distribution to multiple parties, has received much attention recently. Interestingly, CKA can also be performed in a way that protects the identities of the participating parties, therefore providing anonymity. In this work, we propose an anonymous CKA protocol for three parties that is implemented in a highly practical network setting. Specifically, a line of quantum repeater nodes is used to build a linear cluster state among all nodes, which is then used to anonymously establish a secret key between any three of them. The nodes need only share maximally entangled pairs with their neighbours, therefore avoiding the necessity of a central server sharing entangled states. This repeater setup makes our protocol an excellent candidate for implementation in future quantum networks. We explicitly prove that our protocol protects the identities of the participants from one another and perform an analysis of the key rate in the finite regime, contributing to the quest of identifying feasible quantum communication tasks for network architectures beyond point-to-point.
Sharing multi-partite quantum entanglement between parties allows for diverse secure communication tasks to be performed. Among them, conference key agreement (CKA) - an extension of key distribution to multiple parties - has received much attention recently. Interestingly, CKA can also be performed in a way that protects the identities of the participating parties, therefore providing anonymity . In this work, we propose an anonymous CKA protocol for three parties that is implemented in a highly practical network setting. Specifically, a line of quantum repeater nodes is used to build a linear cluster state among all nodes, which is then used to anonymously establish a secret key between any three of them. The nodes need only share maximally entangled pairs with their neighbours, therefore avoiding the necessity of a central server sharing entangled states. This linear chain setup makes our protocol an excellent candidate for implementation in future quantum networks. We explicitly prove that our protocol protects the identities of the participants from one another and perform an analysis of the key rate in the finite regime, contributing to the quest of identifying feasible quantum communication tasks for network architectures beyond point-to-point.
Abstract Anonymous quantum communication (AQC) enables the secure transmission of quantum or classical messages between a sender and a receiver while ensuring the anonymity of their identities. Existing AQC protocols primarily address one-to-one anonymous communication. When there are multiple senders, they must send their messages sequentially to avoid collision problems. In this paper, we propose a multi-participant quantum anonymous communication (MQAC) by employing high-dimensional entangled states. In this protocol, multiple senders establish anonymous entanglement with multiple receivers of their choice and send quantum messages anonymously and simultaneously via quantum teleportation. To propose MQAC, we first present the toolbox we developed, which includes several sub-protocols such as the verification protocol, collision detection protocol, address distribution protocol, and notification protocol. These sub-protocols, which we propose, not only are important parts of MQAC but also serve as the foundation for solving many more complex tasks, such as anonymous commodity transaction. Additionally, the analysis of MQAC demonstrates that neither internal nor external attackers can steal the identities of the communication parties or the transmitted messages by employing any attack. Our work represents an original exploration of anonymous message transmission between multiple senders and receivers in quantum networks.
Quantum Conference Key Agreement (CKA) is a cryptographic effort of multiple parties to establish a shared secret key. While bipartite quantum key distribution protocols are also useful in the context of CKA, multipartite protocols allow for a more efficient generation of the necessary correlations and are therefore viewed favorably in the context of quantum networks. In future quantum networks, generating secret keys in an anonymous way is of tremendous importance for parties that do not only want to keep their shared key secret but also protect their own identity, e.g. in the context of whistle-blowing. In this paper we provide the first protocol for Anonymous Quantum Conference Key Agreement and demonstrate it using four-photon Greenberger-Horne-Zeilinger (GHZ\mathrm{GHZ}GHZ) states.
Conference key agreement (CKA) is a cryptographic effort of multiple parties to establish a shared secret key.In future quantum networks, generating secret keys in an anonymous way is of tremendous importance for parties that want to keep their shared key secret and at the same time protect their own identity.We provide a definition of anonymity for general protocols and present a CKA protocol that is provably anonymous under realistic adversarial scenarios.We base our protocol on shared Greenberger-Horne-Zeilinger states, which have been proposed as more efficient resources for CKA protocols, compared to bipartite entangled resources.The existence of secure and anonymous protocols based on multipartite entangled states provides a new insight on their potential as resources and paves the way for further applications.
Abstract Secret sharing is a procedure for splitting a secret into several parts so that no subset of parts can reconstruct the secret, but the whole set can. In future quantum networks, enabling the splitting of secrets in an anonymous way is of significant importance for splitting secrets among participants while concealing their identities. Generally, multipartite entangled states such as Greenberger‐Horne‐Zeilinger (GHZ) states or W states are used for anonymously splitting secrets due to their symmetry with respect to the parties. However, no particle loss is tolerable for GHZ states, while only one‐particle loss is tolerable for W states in practical quantum networks. In this paper, an anonymous quantum secret sharing (AQSS) protocol is presented by using single particles and Einstein‐Podolsky‐Rosen (EPR) pairs. It is provably anonymous under realistic adversarial scenarios. Due to the anonymity of participants, it naturally removes the risk of participant attack, which is the greatest threat to existing quantum secret sharing (QSS) protocols. The protocol is compared with existing ones and show that it has a higher ability of particle loss tolerance than existing ones based on multipartite entanglement. The existence of anonymous protocols without multipartite entanglement provides an important pathway for practical applications.