Post-quantum zero-trust backbone: Securing critical infrastructure communications against quantum and conventional cyber threats

The convergence of quantum computing capabilities and sophisticated cyberattacks poses unprecedented threats to critical infrastructure communications. Traditional cryptographic defenses and perimeter-based security models are increasingly inadequate against quantum-enabled adversaries and advanced persistent threats targeting operational technology (OT) environments. This paper presents a comprehensive framework for implementing post-quantum cryptography (PQC) within a zero-trust architecture to secure critical infrastructure communications across control centers, substations, hospitals, and ports. Our approach integrates NIST-endorsed quantum-resistant cryptographic suites with identity-first network segmentation, authenticated SCADA protocol encryption, and continuous verification mechanisms. The proposed framework addresses the unique challenges of legacy industrial systems while providing scalable security for hybrid OT/IT environments. Through systematic analysis of current vulnerabilities and implementation strategies, this research demonstrates how a post-quantum zero-trust backbone can prevent catastrophic cyberattacks while maintaining operational continuity in critical infrastructure sectors.