We propose a lightweight post-quantum authentication scheme for multi-hop QKD relay networks, designed to replace client-side mutual transport layer security (TLS) with a more efficient and verifiable mechanism. The protocol combines an additional random source, a Wegman–Carter message authentication code (MAC), and a Dilithium-2 signature, providing 128-bit integrity and strong post-quantum guarantees without relying on client certificates or traditional public key infrastructures. Authentication material is embedded directly into the payload of key forwarding messages, enabling each relay to verify its predecessor in a hop-by-hop fashion. An optional cryptographically verifiable chain allows each relay to attest to the authenticity of previous hops without requiring interactive exchanges or revealing local secrets. This design eliminates the latency and complexity associated with repeated TLS handshakes, while enabling path-level auditing through chained proofs of authenticity. We validate the approach in a hybrid testbed combining simulated trusted nodes with ID Quantique Clavis 3 hardware, where nearly 700 key exchanges were executed across four hops. Experimental results show a 28% reduction in end-to-end latency compared to mutual TLS, stable signature costs below 0.4 ms, and predictable payload growth under chained verification, confirming both practicality and scalability.
We propose a lightweight post-quantum authentication scheme for multi-hop QKD relay networks, designed to replace client-side mutual transport layer security (TLS) with a more efficient and verifiable mechanism. The protocol combines an additional random source, a Wegman–Carter message authentication code (MAC), and a Dilithium-2 signature, providing 128-bit integrity and strong post-quantum guarantees without relying on client certificates or traditional public key infrastructures. Authentication material is embedded directly into the payload of key forwarding messages, enabling each relay to verify its predecessor in a hop-by-hop fashion. An optional cryptographically verifiable chain allows each relay to attest to the authenticity of previous hops without requiring interactive exchanges or revealing local secrets. This design eliminates the latency and complexity associated with repeated TLS handshakes, while enabling path-level auditing through chained proofs of authenticity. We validate the approach in a hybrid testbed combining simulated trusted nodes with ID Quantique Clavis 3 hardware, where nearly 700 key exchanges were executed across four hops. Experimental results show a 28% reduction in end-to-end latency compared to mutual TLS, stable signature costs below 0.4 ms, and predictable payload growth under chained verification, confirming both practicality and scalability.
We present a layered and modular network architecture that combines Quantum Key Distribution (QKD) and Post-Quantum Cryptography (PQC) to provide scalable end-to-end security across long distance multi-hop, trusted-node quantum networks. To ensure interoperability and efficient practical deployment, hop-wise tunnels between physically secured nodes are protected by WireGuard with periodically rotated pre-shared keys sourced via the ETSI GS QKD 014 interface. On top, Rosenpass performs a PQC key exchange to establish an end-to-end data channel without modifying deployed QKD devices or network protocols. This dual-layer composition yields post-quantum forward secrecy and authenticity under practical assumptions. We implement the design using open-source components and validate and evaluate it in simulated and lab test-beds. Experiments show uninterrupted operation over multi-hop paths, low resource footprint and fail-safe mechanisms. We further discuss the design's compositional security, wherein the security of each individual component is preserved under their combination and outline migration paths for operators integrating QKD-aware overlays in existing infrastructures.
Transport Layer Security (TLS) protocols are essential for ensuring the confidentiality, integrity, and authentication of data communications. Mutual authentication between client and server is crucial in high-security scenarios such as finance and government. However, existing TLS protocols typically rely on certificate-based public key infrastructures (PKI) for client authentication, which increases deployment complexity and introduces risks associated with third-party trust. In contrast, password-authenticated TLS protocols use memorable passwords for client authentication, offering advantages in simplicity and usability. Nonetheless, such protocols remain vulnerable to server compromise and fail to provide sufficient security against quantum adversaries.To address these challenges, we propose a novel TLS protocol based on asymmetric password-authenticated key exchange (PAKE). The protocol employs an asymmetric PAKE mechanism wherein only password-derived information is stored on the server, while the client derives its private key from the password. This design effectively mitigates the risk of server leakage attacks. The protocol further integrates two types of post-quantum secure key encapsulation mechanisms (KEMs): an OW-ChCCA (One-Way Checkable against Chosen-Ciphertext Attacks) secure KEM for server key exchange and authentication, and an OW-PCA (One-Way Plaintext-Checkable Attacks) secure KEM for binding the client’s password-derived private key to enable client authentication. Both KEMs support multi-user, multi-challenge settings and admit tight, post-quantum secure instantiations.Furthermore, this paper provides a formal security analysis of the proposed protocol within an optimized multi-stage key exchange model. By combining the random oracle and ideal cipher models with a game-based proof methodology, we demonstrate that the protocol achieves mutual authentication and forward secrecy, while also providing tight security bounds and post-quantum resilience. This work thus presents a promising solution for constructing post-quantum password-authenticated TLS protocols.
Modern instant messaging systems require end-to-end (E2E) security guarantees while operating over server-mediated infrastructures that cannot be fully trusted. At the same time, the impending transition to post-quantum cryptography raises nontrivial challenges for the design of secure messaging protocols that preserve these guarantees. In this work, we present the design of a post-quantum end-to-end secure protocol for instant messaging applications under an untrusted relay model. The proposed construction relies on lattice-based primitives standardized by NIST, namely ML-KEM for key establishment and ML-DSA for authentication, and follows a Double-KEM pattern combined with explicit context binding to derive an E2E session key known only to the communicating clients. The server acts solely as an authenticated relay and never gains access to plaintext messages or session keys. In addition to the protocol design, we complement the protocol description with an automated symbolic verification using ProVerif, establishing injective mutual authentication and session-key secrecy under a Dolev–Yao adversary model. Finally, we characterize the computational cost of different authentication and verification policies and evaluate the performance of the handshake on heterogeneous cloud-based architectures. The results provide practical insight into the feasibility of deploying post-quantum end-to-end secure protocols within existing instant messaging infrastructures.
Current quantum communication protocols rely heavily on classical authentication for message origin verification, leaving them vulnerable to evolving attacks that exploit classical trust assumptions. In this work, we propose a novel framework for secure quantum relay networks that completely avoids classical authentication. Instead, we leverage pre-distributed entanglement graphs and non-classical correlation-assisted decoding to enable exclusive message retrieval by designated nodes without broadcasting any key or handshake. The system routes messages across multiple relay nodes, yet ensures that no intermediate node can access the message unless it possesses the entangled state partner. We demonstrate that even in multi-path scenarios with asynchronous entanglement distribution, the protocol guarantees quantum-forward secrecy and end-to-end origin integrity without trusted intermediaries. Simulation results confirm both functionality and robustness under entanglement loss and imperfect detection. This architecture paves the way for scalable quantum communication systems where physical quantum states replace classical authentication mechanisms entirely.
Post-quantum cryptography (PQC) and quantum key distribution (QKD) address the quantum threat from opposite directions: PQC replaces vulnerable public-key algorithms with schemes believed to resist quantum cryptanalysis, while QKD derives keys whose secrecy rests on physical assumptions rather than computational ones. Because each approach has a distinct failure mode, a growing body of work combines them so that a session key remains secure if either component holds. We first establish the deployed baseline, hybrid classical-plus-PQC key exchange, against which QKD-augmented designs must be judged. We then propose a taxonomy of hybrid PQC-QKD designs along eight dimensions (integration layer, combiner construction, authentication scope and source, QKD topology, trusted entities, key-delivery interface, classical component, and evidence type), and use it to compare published protocols, including Muckle and its successors, MACsec and TLS integrations, and IKEv2 mechanisms standardised in RFCs 8784, 9370, and 9867. We examine key-combiner constructions in light of the KEM-combiner literature and of NIST, ETSI, and ITU-T guidance, and map the security arguments for hybrid PQC-QKD protocols onto a common grid of security model, assumptions, permitted compromise, established guarantee, and limitations. We synthesise deployment evidence from metropolitan and national QKD networks, distinguishing the few testbeds that have run PQC in the key path from pure-QKD deployments, and summarise the standards and policy landscape, including the positions of national security agencies that recommend against relying on QKD alone. We close with open problems: authentication of the QKD classical channel, shared-infrastructure threat models, device certification versus formal proofs, formal verification of hybrid handshakes, and the lack of peer-reviewed deployment economics.
Quantum Key Distribution (QKD) offers information-theoretic security for key exchange; however, its effective implementation is contingent upon the security of the classical communication channel, especially for authentication purposes. This work presents a system-level study of quantum-safe authentication for the classical channel in multi-site QKD networks, comparing two post-quantum cryptographic (PQC) approaches within a unified evaluation framework: one based on lattice-based digital signatures, and one based on message authentication codes (MACs) bootstrapped by PQC key establishment. We develop a multi-site network model to analyze the scalability and deployment limitations of traditional pre-shared key methods. The framework is evaluated using both simulations and hardware-based experiments, considering communication cost, computational overhead, and the impact on the key generation rate. The results show that signature-based authentication offers stateless per-message verification at a higher per-block cost, while MAC-based authentication is better suited to high-throughput environments, both at the same linear onboarding cost. The study quantifies the trade-offs between security, scalability, and performance, and provides practical guidance for deploying quantum-safe authentication in real-world QKD systems.