Quantum Safe Networks: A Case Study on Securing QKD Interfaces Using PQC

Quantum-Safe Networks (QSNs) use quantum key distribution (QKD) to deliver keys generated using a Quantum Random Number Generator (QRNG) to consumers at scale. In practice, prevailing Quantum-Key-as-a-Service (QKaaS) offerings still assume that each consumer site deploys on-premise QKD hardware, creating cost and feasibility barriers that limit adoption. Although ETSI GS QKD 014 standardizes APIs for key retrieval between Secure Application Entities (SAEs) and Key Management Entities (KMEs), it does not address key delivery across untrusted classical networks to consumers without local QKD devices. We close this gap with a gateway architecture that transparently secures ETSI-compliant QKD APIs using Post-Quantum Cryptography (PQC)—applying PQC signatures and key-encapsulation mechanisms end-to-end—without requiring changes to existing devices or software. The design supports cryptographic agility, enabling runtime selection and rotation among standardized PQC schemes. Evaluations on both simulated QKD environments and production-grade hardware show minimal overhead ($\approx 1.3\times$–1.5× versus baseline) and robust scaling across concurrent connections and multiple consumer sites, extending the reach of QSNs beyond premises equipped with QKD while preserving end-to-end quantum-safe guarantees. Overall, this paper equips practitioners with a systematized view of PQC–QKD integration in QSNs, with an actionable gateway blueprint for extending QSNs without the need for on-premise QKD deployments.