Quantum Key Distribution for Power Systems Achieves Feasibility with Defined Security Costs and Outage Probability

Modern power systems, increasingly reliant on digital communication, face growing vulnerability to cyberattacks, prompting a need for exceptionally secure communication networks. Ziqing Zhu, from IEEE, and colleagues address this challenge by developing a comprehensive framework to assess the economic and technical viability of Quantum Key Distribution (QKD) for protecting power-system communications. Their work establishes analytical conditions for reliable operation, considering factors like key demand, signal loss, and backup security measures, and introduces new metrics to unify the costs associated with security investments. Through detailed simulations using realistic power-system models, the researchers demonstrate that combining QKD with existing security protocols significantly improves network availability and reduces the risk of communication failures, identifying specific network conditions where QKD becomes a cost-effective solution for enhancing the resilience of future power infrastructure.

The study highlights the reliance of power systems on digital communications and the need for robust, future-proof security solutions. The core of this work centers on QKD, a technology that generates and distributes encryption keys using the principles of quantum mechanics, making eavesdropping detectable. Rather than replacing existing cryptography entirely, the researchers propose a hybrid system combining QKD with post-quantum cryptography (PQC) to provide layered security.

A sophisticated mathematical model simulates a QKD-enhanced communication network, considering key demand, supply rates, buffering capabilities, and network conditions. Techno-economic analysis played a crucial role, with scientists developing metrics to evaluate the cost-effectiveness of QKD, including capital expenditures, operational expenses, and risk-related costs. The Levelized Cost of Security (LCoS) metric calculates the total cost of security over the system’s lifetime, while the Cost of Incremental Security (CIS) evaluates the additional cost of adding QKD to an existing infrastructure. Simulations under realistic scenarios demonstrate that hybrid systems offer a significant improvement in security compared to relying on either technology alone, emphasizing the importance of buffering and fallback mechanisms for continuous operation.

While currently expensive, the economic viability of QKD depends on factors like fiber attenuation, buffer design, and key lifecycle policies, with investment in high-quality optical fiber significantly reducing overall costs. The findings reveal that in scenarios with escalating cyber threats, PQC-only systems become increasingly vulnerable, while QKD-enhanced systems maintain a higher level of security. Reducing the capital expenditure on QKD systems makes them more economically competitive. Scientists developed a stochastic system model that simultaneously captures time-varying key demand, QKD supply constrained by optical loss, station-side buffering capabilities, and post-quantum cryptography (PQC) fallback mechanisms, providing analytical conditions for ensuring service-level assurance, including buffer stability, outage probability, and availability bounds. To quantify security benefits, the team formulated two novel metrics: Levelized Cost of Security (LCoSec) and Cost of Incremental Security (CIS). These metrics integrate capital expenditure, operational expenses, and quantifiable risk costs within a discounted net-present-value framework, allowing for meaningful comparisons between different security architectures.

Researchers normalized secure output by service level agreements to enable threshold-based decision-making and cross-architecture comparisons. The study employed discrete-event simulations using three representative test systems, mirroring existing electrical topologies in metropolitan backbones, distribution-level hubs, and long-haul interconnects. Simulations incorporated standard-compliant traffic profiles and disturbance scripts to realistically model network conditions. Scientists evaluated PQC-only, QKD-only, and hybrid architectures, assessing availability, delay violations, key exhaustion, and economic metrics under realistic device performance curves.

Comprehensive sensitivity analyses quantified the impact of parameters like fiber loss, buffer thresholds, refresh rates, pricing structures, and threat scenarios on both SLA compliance and lifecycle costs. This work delivers a fully reproducible evaluation pipeline, facilitating rapid updating and scenario testing. Experimental results demonstrate that hybrid architectures, dominated by QKD, effectively absorb supply fluctuations and suppress tail risks in high-real-time and long-duration confidentiality applications. Researchers developed a stochastic system model that captures the dynamic interplay between time-varying key demand, QKD supply constrained by optical loss, station-side buffering, and post-quantum cryptography fallback mechanisms. Analytical conditions were derived to assure service-level performance, specifically demonstrating conditions for buffer stability, outage probability, and availability bounds. To quantify security investments, the team formulated two key metrics: Levelized Cost of Security (LCoSec) and Cost of Incremental Security (CIS).

These metrics unify capital, operational, and risk-related expenditures within a discounted net-present-value framework, allowing for direct comparison of different security architectures. The framework was applied to three test systems, representing metropolitan, distribution, and long-haul networks, using realistic communication topologies and standard-compliant traffic profiles. Discrete-event simulations comparing PQC-only, QKD-only, and hybrid architectures revealed that hybrid systems, dominated by QKD, significantly reduce key-outage probability and SLA shortfalls, achieving near-unit availability for real-time and confidentiality-critical services. Economic analyses identified clear breakeven zones where QKD-enhanced deployments become cost-effective, particularly in metropolitan and distribution-level networks under moderate optical loss and with appropriately sized buffers. Sensitivity analyses demonstrated the impact of parameters like fiber loss, buffer thresholds, and refresh rates on both SLA compliance and lifecycle costs, pinpointing the conditions that optimize the cost-benefit landscape. The team developed a stochastic model that accounts for fluctuating key demands, limitations in QKD supply due to optical signal loss, and the need for buffer storage and fallback to traditional cryptographic methods. Through detailed simulations using realistic power system network models, the study demonstrates that hybrid architectures, combining QKD.