The advent of quantum computing threatens classical cryptographic mechanisms, demanding new strategies for securing communication networks. Since real-world networks cannot be fully Quantum Key Distribution (QKD)-enabled due to infrastructure constraints, practical security solutions must support hybrid operation. This paper presents an adaptive security framework that enables quantum-safe communications across real-world heterogeneous networks by combining QKD and Post-Quantum Cryptography (PQC). Building upon a hierarchical key management architecture with Virtual Key Management Systems (vKMS) and a centralized Quantum Security Controller (QuSeC), the framework dynamically assigns security levels based on node capabilities. By transitioning between pure QKD, hybrid, and PQC modes, it ensures end-to-end quantum-safe protection regardless of the underlying node capabilities. The framework has been implemented and validated on a Kubernetes-based containerized testbed, demonstrating robust operation and performance across all scenarios. Results highlight its potential to support the gradual integration of quantum-safe technologies into existing infrastructures, paving the way toward fully quantum-safe communication networks.
The advent of quantum computing threatens classical cryptographic mechanisms, demanding new strategies for securing communication networks. Since real-world networks cannot be fully Quantum Key Distribution (QKD)-enabled due to infrastructure constraints, practical security solutions must support hybrid operation. This paper presents an adaptive security framework that enables quantum-safe communications across real-world heterogeneous networks by combining QKD and Post-Quantum Cryptography (PQC). Building upon a hierarchical key management architecture with Virtual Key Management Systems (vKMS) and a centralized Quantum Security Controller (QuSeC), the framework dynamically assigns security levels based on node capabilities. By transitioning between pure QKD, hybrid, and PQC modes, it ensures end-to-end quantum-safe protection regardless of the underlying node capabilities. The framework has been implemented and validated on a Kubernetes-based containerized testbed, demonstrating robust operation and performance across all scenarios. Results highlight its potential to support the gradual integration of quantum-safe technologies into existing infrastructures, paving the way toward fully quantum-safe communication networks.
Abstract: This study advances a unifying systems perspective on quantum-safe network security by synthesizing recent progress in quantum cryptography with practical integration patterns across carrier-grade infrastructures. Concept analysis distinguishes the roles of quantum key distribution (QKD), device-independent variants, quantum authentication, and post-quantum cryptography (PQC) within zero-trust architectures. Building on this, a layered framework—spanning physical/entanglement resources, key management, crypto-agility, control plane orchestration, and policy/compliance—is articulated to support end-to-end, composable guarantees. The problem addressed is the realization of verifiable, quantum-resilient security under operational constraints involving latency, key-rate variability, and heterogeneous trust assumptions. Methodology combines a structured literature synthesis with formal composability mapping to universal composability principles, adversarial threat modeling for quantum-enabled attackers, and testbed/simulation evaluation of hybrid QKD–PQC pipelines across L2–L3 segments and 5G/6G backhaul scenarios. Key results indicate that (i) selective QKD deployment on high-value links coupled with PQC at endpoints enhances resilience while preserving crypto-agility; (ii) automated key-lifecycle orchestration reduces exposure windows; and (iii) device-independent assurances strengthen guarantees where trust relaxation is necessary. The impact is a deployment-ready reference architecture, measurable integration metrics, and guidance aligned with emerging standards for critical infrastructure and national networks. The implications extend to procurement, compliance, and roadmap planning for quantum-era network security. Keywords: quantum-safe cryptography, quantum key distribution (QKD), post-quantum cryptography (PQC), hybrid QKD–PQC, composable security, device-independent QKD, zero-trust networks, key management and orchestration, 5G/6G backhaul, network security architecture, standards and interoperability
With the advent of quantum computing, the increasing threats to security poses a great challenge to communication networks. Recent innovations in this field resulted in promising technologies such as Quantum Key Distribution (QKD), which enables the generation of unconditionally secure keys, establishing secure communications between remote nodes. Additionally, QKD networks enable the interconnection of multi-node architectures, extending the point-to-point nature of QKD. However, due to the limitations of the current state of technology, the scalability of QKD networks remains a challenge toward feasible implementations. When it comes to long-distance implementations, trusted relay nodes partially solve the distance issue through the forwarding of the distributed keys, allowing applications that do not have a direct QKD link to securely share key material. Even though the relay procedure itself has been extensively studied, the establishment of the relaying node path still lacks a solution. This paper proposes an innovative network architecture that solves the challenges of Key Management System (KMS) identification, relay path discovery, and scalability of QKD networks by integrating Software-Defined Networking (SDN) principles, and establishing high-level virtual KMSs (vKMS) in each node and creating a new entity called the Quantum Security Controller (QuSeC). The vKMS serves the end-user key requests, managing the multiple KMSs within the node and abstracting the user from discovering the correct KMS. Additionally, based on the high-level view of the network topology and status, the QuSeC serves the path discovery requests from vKMSs, computing the end-to-end (E2E) relay path and applying security policies. The paper also provides a security analysis of the proposal, identifying the security levels of the architecture and analyzing the core networking security properties, and a performance evaluation that confirms the feasibility and scalability of the proposal.
Advances in quantum computing pose a significant threat to the widely used Public Key Infrastructure (PKI). The two leading technologies to address this challenge are Post-Quantum Cryptography and Quantum Key Distribution. A promising approach is the hybridization of these technologies - combining their respective strengths while mitigating their limitations - and integrating them with the cryptographic mechanisms used today to enhance crypto-agility and facilitate transitioning to a quantum-safe infrastructure. However, changing current network protocols to quantum-safe alternatives is not just a matter of security: their efficiency and scalability must also be demonstrated within real-world telecommunications infrastructures to ensure their practical adoption. In this work, we present the first long-running test with detailed measurements of a suite of hybrid quantum-safe protocols that integrate classical cryptography, PQC, and QKD within a production environment (MadQCI). Using standardized protocols and interfaces and employing Transport Layer Security (TLS) as the base protocol for real-world comparison, this study demonstrates the efficiency and scalability of the proposed solution in deployed heterogeneous networks. These results mark a significant step towards the widespread adoption of quantum-safe hybrid protocols and contribute to clarifying the path toward their future standardization in next-generation telecommunications networks.
The advent of quantum computing imposes unprecedented risks on conventional cryptosystems, necessitating novel secure communication strategies. This work presents a modular, hybrid, and adaptive protocol that integrates Quantum Key Distribution (QKD) with Post-Quantum Cryptography (PQC) to maintain continuous, Quantum-Safe Key Exchanges, even under adverse network conditions that typically hinder the state-of-the-art QKD-based methods. At its core are specialized Crypto-Machines, which incorporate QKD Nodes compliant with ETSI-14 standards and modular PQC components, thereby supporting seamless transitions among lattice-, hash-, or code-based schemes. A signed, Quantum-Resistant, HOTP-based mechanism ensures robust mutual authentication. When QKD utilization becomes infeasible—due to, for example, fiber tampering—the protocol dynamically shifts to PQC, safeguarding ongoing communications. Once a key is established, AES-256-GCM encryption provides strong data confidentiality. Simulations have been conducted with the SeQUeNCe toolkit to demonstrate the protocol’s adaptability and resilience. The results show how Crypto-Machines are able to provide QKD exchanges under favorable network conditions while also being able to fall-back to PQC-based approaches with a minimal impact on the performance. Hence, the proposed stack allows operators to maintain Quantum-Proof Key Exchanges where current state-of-the-art solutions are impaired by a low-quality network connection, and thereby offering a forward-looking security framework suited to the quantum era
The emergence of Cryptographically Relevant Quantum Computers (CRQCs) presents a critical threat to classical cryptographic systems, particularly widely adopted protocols such as RSA, Diffie-Hellman (DH), and Elliptic Curve Cryptography (ECC). Given their extensive use in the financial sector, the advent of quantum adversaries compels banking institutions to proactively develop and adopt quantum-safe communication mechanisms. This paper introduces a hybrid quantum-safe architecture, orchestrated via Software-Defined Networking (SDN) key distribution. The proposed framework enables the early integration of Classical Cryptography (CC), Quantum Key Distribution (QKD), and Post-Quantum Cryptography (PQC) within a Dynamic Multipoint Virtual Private Network (DMVPN) environment, providing highly scalable, full-mesh, site-to-site encrypted communications for enterprise networks. This is particularly relevant at a time when PQC algorithms have not yet been incorporated into finalized IPsec standards. The architecture has been validated across a five-node testbed comprising three physical nodes within a campus network in Madrid and two private-cloud nodes located in the north of Spain and Mexico. The deployment leverages a heterogeneous mix of physical and virtual devices, diverse technology providers, Discrete Variable QKD (DV-QKD) and Continuous Variable QKD (CV-QKD) implementations, and mutually incompatible key-delivery interfaces (ETSI004, ETSI014 and Cisco SKIP), demonstrating flexibility, scalability, and interoperability across environments. Through this framework, we demonstrate that quantum-safe communication in financial networks is not only technically feasible but also scalable, interoperable, and resilient. The proposed architecture establishes a robust, flexible, and future-proof foundation for secure financial communications in the era of quantum computing.
Abstract Advances in quantum computing pose a significant threat to the widely used Public Key Infrastructure (PKI). The two leading technologies to address this challenge are Post-Quantum Cryptography and Quantum Key Distribution. A promising approach is the hybridization of these technologies - combining their respective strengths while mitigating their limitations - and integrating them with the cryptographic mechanisms used today to enhance crypto-agility and facilitate transitioning to a quantum-safe infrastructure. However, changing current network protocols to quantum-safe alternatives is not just a matter of security: their efficiency and scalability must also be demonstrated within real-world telecommunications infrastructures to ensure their practical adoption. In this work, we present the first long-running test with detailed measurements of a suite of hybrid quantum-safe protocols that integrate classical cryptography, PQC, and QKD within a production environment (MadQCI). Using standardized protocols and interfaces and employing Transport Layer Security (TLS) as the base protocol for real-world comparison, this study demonstrates the efficiency and scalability of the proposed solution in deployed heterogeneous networks. These results mark a significant step towards the widespread adoption of quantum-safe hybrid protocols and contribute to clarifying the path toward their future standardization in next-generation telecommunications networks.