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Radiotekhnika

Problems and prospects of building authentication methods in quantum key distribution channels

Yevgen V. Kotukh, Maksym Korobchynskyi, Valerii Kozlovskyi, Gennady Khalimov, С.О. Кудренко, Діана Козловська

Published Jul 25, 2026• 0 citations
Publisher

Abstract

The paper addresses entity authentication in quantum key distribution (QKD) systems as a decisive condition of their practical security. It is shown that the information-theoretic security of quantum key agreement does not eliminate the need to authenticate the communicating parties: an unauthenticated classical channel leaves the system exposed to the man-in-the-middle attack, since the eavesdropper can run independent QKD instances with each party and reconcile two keys under full control. Existing authentication methods are analysed and classified by the underlying cryptographic primitive: symmetric schemes based on Wegman–Carter universal hashing, pre-shared and fixed keys, public-key infrastructure, two-way authentication, quantum entity/identity authentication, and zero-knowledge proofs. For each class the operating principle, advantages and limitations are determined, with emphasis on key management, scalability and trust distribution. It is established that symmetric and quantum-layer methods rely on pre-shared secrets with a quadratic growth of key material, public-key infrastructure introduces a single trust bottleneck and quantum-vulnerable primitives, while existing zero-knowledge authentication schemes are quantum and bound to the physical layer or solve network properties other than identity. A comparative analysis reveals an unresolved scientific gap: the absence of a scalable entity-authentication method that simultaneously provides non-disclosure of the secret, quantum resistance, sub-quadratic scalability and minimisation of trust assumptions. On this basis, a prospective research direction is substantiated – the construction of entity-authentication methods based on post-quantum zero-knowledge proofs operating over the classical control plane of scalable QKD networks. The requirements for such a method are formulated, and its compatibility with formal QKD security proofs is discussed.

DOI
10.30837/rt.2026.2.225.08

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The paper addresses entity authentication in quantum key distribution (QKD) systems as a decisive condition of their practical security. It is shown that the information-theoretic security of quantum key agreement does not eliminate the need to authenticate the communicating parties: an unauthenticated classical channel leaves the system exposed to the man-in-the-middle attack, since the eavesdropper can run independent QKD instances with each party and reconcile two keys under full control. Existing authentication methods are analysed and classified by the underlying cryptographic primitive: symmetric schemes based on Wegman–Carter universal hashing, pre-shared and fixed keys, public-key infrastructure, two-way authentication, quantum entity/identity authentication, and zero-knowledge proofs. For each class the operating principle, advantages and limitations are determined, with emphasis on key management, scalability and trust distribution. It is established that symmetric and quantum-layer methods rely on pre-shared secrets with a quadratic growth of key material, public-key infrastructure introduces a single trust bottleneck and quantum-vulnerable primitives, while existing zero-knowledge authentication schemes are quantum and bound to the physical layer or solve network properties other than identity. A comparative analysis reveals an unresolved scientific gap: the absence of a scalable entity-authentication method that simultaneously provides non-disclosure of the secret, quantum resistance, sub-quadratic scalability and minimisation of trust assumptions. On this basis, a prospective research direction is substantiated – the construction of entity-authentication methods based on post-quantum zero-knowledge proofs operating over the classical control plane of scalable QKD networks. The requirements for such a method are formulated, and its compatibility with formal QKD security proofs is discussed.
Quantum Key Distribution (QKD) is a secret key agreement technique that consists of two parts: quantum transmission and measurement on a quantum channel, and classical post-processing on a public communication channel. It enjoys provable unconditional security provided that the public communication channel is immutable. Otherwise, QKD is vulnerable to a man-in-the-middle attack. Immutable public communication channels, however, do not exist in practice. So we need to use authentication that implements the properties of an immutable channel as well as possible. One scheme that serves this purpose well is the Wegman-Carter authentication (WCA), which is built upon Almost Strongly Universal2 (ASU2) hashing. This scheme uses a new key in each authentication attempt to select a hash function from an ASU2 family, which is then used to generate the authentication tag for a message. The main focus of this dissertation is on authentication in the context of QKD. We study ASU2 hash functions, security of QKD that employs a computationally secure authentication, and also security of authentication with a partially known key. Specifically, we study the following. First, Universal hash functions and their constructions are reviewed, and as well as a new construction of ASU2 hash functions is presented. Second, security of QKD that employs a specific computationally secure authentication is studied. We present detailed attacks on various practical implementations of QKD that employs this authentication. We also provide countermeasures and prove necessary and sufficient conditions for upgrading the security of the authentication to the level of unconditional security. Third, Universal hash function based multiple authentication is studied. This uses a fixed ASU2 hash function followed by one-time pad encryption, to keep the hash function secret. We show that the one-time pad is necessary in every round for the authentication to be unconditionally secure. Lastly, we study security of the WCA scheme, in the case of a partially known authentication key. Here we prove tight information-theoretic security bounds and also analyse security using witness indistinguishability as used in the Universal Composability framework.
The security of quantum cryptography relies on the foundations of quantum mechanics, in contrast to traditional public key cryptography which relies on the computational difficulty of certain mathematical functions, and cannot provide any indication of eavesdropping or guarantee of key security. The proposal present in this work develops a quantum key distribution model to safeguard security in large networks, in the directions of classical cryptography and quantum cryptography. Two three-party Quantum key distribution are used in this model, one with implicit user authentication and the other with explicit mutual authentication, are proposed to demonstrate the merits of the new combination. The performance of Quantum Key Distribution (QKD) systems have notably progressed since the early experimental demonstrations. The current evolutions in QKD research indicate that the pace of this progression is very likely to be maintained, if not increased, in the future years. In parallel to these improvements of QKD techniques, commercial products are also being developed, making QKD deployment a feasible alternative for securing real data networks. Deployment of a real QKD network is however far from being straightforward. It requires development of a network architecture connecting multiple users that may possibly be very far away from each other. Considering the fact that the existing QKD links are only point-to-point, and intrinsically limited in distance, deployment of a practical QKD network structure is a nontrivial problem. The proposed work describes the proposed architecture for a QKD network specify the requirements relevant to the network design, protocols, and services. The objective of this specification is to define the major components and their main features The proposal provides security against such attacks as man-in-the-middle, eavesdropping and replay. It also improves the efficiency of the quantum key distribution which contains the fewest number of communication rounds among existing Quantum key distributions. In this model two parties can share and use a long-term secret (repeatedly). To prove the security of the proposed schemes, this proposed model provides a primitive called the Unbiased-Chosen Basis (UCB) assumption with the quantum key in angular positions.
Quantum key distribution (QKD) promises secure key agreement by using quantum mechanical systems. We argue that QKD will be an important part of future cryptographic infrastructures. It can provide long-term confidentiality for encrypted information without reliance on computational assumptions. Although QKD still requires authentication to prevent man-in-the-middle attacks, it can make use of either information-theoretically secure symmetric key authentication or computationally secure public key authentication: even when using public key authentication, we argue that QKD still offers stronger security than classical key agreement. 1
Abstract Quantum key distribution (QKD) can provide information theoretically secure key exchange even in the era of quantum computers. However, QKD requires the classical channel to be authenticated, the current method for which is pre-sharing symmetric keys. For a QKD network of n users, this method requires Cn2=n(n−1)/2{C}_{n}^{2}=n(n-1)/2Cn2​=n(n−1)/2 C n 2 = n ( n − 1 ) / 2 pairs of symmetric keys to realize pairwise interconnection. In contrast, with the help of a mature public key infrastructure (PKI) and post-quantum cryptography (PQC) with quantum-resistant security, each user only needs to apply for one digital certificate from a certificate authority (CA) to achieve efficient and secure authentication for QKD. We need to assume only the short-term security of the PQC algorithm to achieve long-term security of the distributed keys. Here, we experimentally verified the feasibility, efficiency, and stability of the PQC algorithm in QKD authentication, and demonstrated the advantages when new users join the QKD network. Using the PQC public-key infrastructure, the nodes need to mutually trust only the CA to authenticate each other. QKD combined with PQC authentication will greatly promote and extend the application prospects of quantum-safe communication.
Quantum Key Distribution (QKD) protocols, such as BB84, require secure authentication of their classical communication channel to ensure message integrity and authenticity, which is fundamental to successfully distribute unconditionally secure keys and prevent critical vulnerabilities. Traditionally, QKD relies on pre-shared secret keys for this authentication, posing significant scalability challenges. Employing asymmetric encryption methods is also not a viable alternative, as these methods are either vulnerable to quantum computing attacks or lack rigorous security proofs. To address these issues, we propose using the well-established Kerberos authentication protocol, which relies on symmetric cryptography inherently resistant to known quantum attacks, to securely distribute symmetric session keys that authenticate classical communication in QKD systems. We demonstrate the feasibility and practical security advantages of employing Kerberos-generated session keys, inherently resistant to quantum computing attacks, without modifying existing Kerberos workflows, providing a practical quantum-secure solution that leverages existing IT infrastructure.
Quantum key distribution (QKD) can provide information theoretically secure key exchange even in the era of quantum computer. However, QKD requires the classical channel to be authenticated, and the current method is pre-sharing symmetric keys. For a QKD network of nnn users, this method requires Cn2=n(n−1)/2C_n^2 = n(n-1)/2Cn2​=n(n−1)/2 pairs of symmetric keys to realize pairwise interconnection. In contrast, with the help of mature public key infrastructure (PKI) and post-quantum cryptography (PQC) with quantum resistant security, each user only needs to apply for a digital certificate from certificate authority (CA) to achieve efficient and secure authentication for QKD. We only need to assume the short-term security of the PQC algorithm to achieve the long-term security of the distributed keys. Here, we experimentally verified the feasibility, efficiency and stability of the PQC algorithm in QKD authentication, and demonstrated the advantages when new users join the QKD network. Using PQC authentication we only need to believe the CA is safe, rather than all trusted relays. QKD combined with PQC authentication will greatly promote and extend the application prospects of quantum safe communication.