Public Key Infrastructures (PKIs) are foundational to time- and security-critical systems such as air traffic management and cooperative intelligent transport systems (C-ITS). These PKIs rely almost exclusively on classical public-key cryptography, which will become vulnerable once cryptographically relevant quantum computers emerge. Migrating such systems to post-quantum cryptography (PQC) is therefore necessary but non-trivial, as these environments impose strict constraints on latency, bandwidth, interoperability, long system lifetimes, and regulatory compliance. This paper presents a comparative, constraint-driven analysis of PQC migration for time- and security-critical PKIs. Focusing on System-Wide Information Management (SWIM) and C-ITS, we examine how PQC signature and key sizes, verification costs, and certificate structures affect real-time communication, certificate validation, and session establishment. In particular, we analyze the impact of certificate size growth and verification latency on time-critical messaging using published benchmarks and protocol specifications. Rather than proposing new cryptographic primitives or implementations, this work synthesizes existing benchmarks, standardization documents, and protocol specifications to identify feasibility limits, migration risks, and design trade-offs. The analysis shows that certificate chain length and signature overhead can dominate session establishment time in short communication windows, particularly in C-ITS environments, even when individual cryptographic operations remain computationally efficient. We further discuss the operational risks introduced by hybrid cryptographic deployments, including increased system complexity, negotiation failures, and insecure fallback behavior. In addition, we highlight how long system lifetimes and slow standardization cycles in safety-critical sectors complicate timely cryptographic transitions. The results indicate that migration feasibility is often determined by system-level constraints, such as certificate handling, protocol overhead, interoperability requirements, and regulatory alignment, rather than by the performance of individual PQC algorithms alone. Based on this analysis, we present a benchmarking-based migration framework tailored to critical PKIs, highlighting where hybrid cryptographic approaches are unavoidable, where they introduce new risks, and which classes of PQC algorithms are conditionally viable under strict timing and bandwidth constraints. The paper concludes with concrete recommendations for system designers and policymakers to support crypto-agile PQC migration without compromising operational safety.
Public Key Infrastructures (PKIs) are foundational to time- and security-critical systems such as air traffic management and cooperative intelligent transport systems (C-ITS). These PKIs rely almost exclusively on classical public-key cryptography, which will become vulnerable once cryptographically relevant quantum computers emerge. Migrating such systems to post-quantum cryptography (PQC) is therefore necessary but non-trivial, as these environments impose strict constraints on latency, bandwidth, interoperability, long system lifetimes, and regulatory compliance. This paper presents a comparative, constraint-driven analysis of PQC migration for time- and security-critical PKIs. Focusing on System-Wide Information Management (SWIM) and C-ITS, we examine how PQC signature and key sizes, verification costs, and certificate structures affect real-time communication, certificate validation, and session establishment. In particular, we analyze the impact of certificate size growth and verification latency on time-critical messaging using published benchmarks and protocol specifications. Rather than proposing new cryptographic primitives or implementations, this work synthesizes existing benchmarks, standardization documents, and protocol specifications to identify feasibility limits, migration risks, and design trade-offs. The analysis shows that certificate chain length and signature overhead can dominate session establishment time in short communication windows, particularly in C-ITS environments, even when individual cryptographic operations remain computationally efficient. We further discuss the operational risks introduced by hybrid cryptographic deployments, including increased system complexity, negotiation failures, and insecure fallback behavior. In addition, we highlight how long system lifetimes and slow standardization cycles in safety-critical sectors complicate timely cryptographic transitions. The results indicate that migration feasibility is often determined by system-level constraints, such as certificate handling, protocol overhead, interoperability requirements, and regulatory alignment, rather than by the performance of individual PQC algorithms alone. Based on this analysis, we present a benchmarking-based migration framework tailored to critical PKIs, highlighting where hybrid cryptographic approaches are unavoidable, where they introduce new risks, and which classes of PQC algorithms are conditionally viable under strict timing and bandwidth constraints. The paper concludes with concrete recommendations for system designers and policymakers to support crypto-agile PQC migration without compromising operational safety.
Abstract The prospect of cryptanalytically relevant quantum computers (CRQCs) motivates a transition from classical cryptography to post-quantum cryptography (PQC). Shor’s algorithm threatens widely deployed public-key schemes used for key establishment and digital signatures, while Grover’s algorithm reduces effective security margins for symmetric-key and hash-based primitives. The harvest-now, decrypt-later (HNDL) threat further increases urgency because adversaries can store encrypted data today for future decryption, placing long-lived confidentiality requirements and trust infrastructure at risk. This survey frames PQC adoption as a standards-to-deployment program. We review the PQC design space and summarize deployment-critical constraints, including handshake and certificate size growth, latency under network loss, computational cost, memory and storage requirements, implementation complexity, and side-channel robustness. We then present an iterative migration pipeline covering cryptographic inventory, risk-based prioritization using data sensitivity and cryptoperiod, algorithm and parameter profile selection, hybrid classical and PQC constructions for backward compatibility, pilot validation with measurable go/no-go criteria, and long-term operations with crypto-agility. Finally, we connect standardization outputs to concrete integration surfaces and illustrate the workflow across transport layer security (TLS) and the web public key infrastructure (Web PKI), virtual private networks (VPNs) and internet protocol security (IPsec), and constrained Internet of things (IoT) deployments, and we summarize open challenges in interoperability, public key infrastructure (PKI) transition mechanics, implementation maturity and operational governance.
The transition to post-quantum cryptography presents enterprises with a complex systems-engineering challenge extending beyond algorithm replacement. Transport Layer Security, public key infrastructure, virtual private networks, cloud-native platforms, identity services, and machine-to-machine communications depend on interconnected cryptographic libraries, certificates, protocols, hardware modules, policies, and vendor products. This review examines crypto-agile migration to hybrid post-quantum cryptography, where classical and quantum-resistant mechanisms are combined to preserve established assurance while emerging algorithms and implementations mature. It develops a migration-oriented taxonomy covering cryptographic discovery, dependency mapping, hybrid key establishment, composite authentication, certificate lifecycle management, protocol negotiation, performance optimization, interoperability testing, and operational governance. Particular attention is given to larger keys, ciphertexts, and signatures; handshake fragmentation; certificate-chain expansion; hardware acceleration; legacy compatibility; downgrade resistance; and observability across distributed environments. The review compares migration requirements in enterprise TLS, PKI, remote-access and site-to-site VPNs, service meshes, API gateways, container platforms, serverless services, secrets systems, and multicloud infrastructures. It also analyzes staged deployment patterns, including inventory-first modernization, proxy-based termination, dual certificates, hybrid tunnels, algorithm-policy abstraction, and controlled fallback. Evaluation criteria integrate security, interoperability, latency, throughput, bandwidth, memory, certificate issuance, operational resilience, and rollback readiness. The findings indicate that successful migration depends on treating cryptography as a continuously governed enterprise capability rather than a fixed protocol configuration. The paper concludes by identifying gaps in standardization, automated discovery, cross-vendor testing, cryptographic telemetry, constrained-device support, and lifecycle evidence, providing organizations with a structured foundation for prioritized, reversible, and verifiable post-quantum transformation across heterogeneous digital services. Keywords: Crypto-Agility, Hybrid Cryptography, Post-Quantum Cryptography, Public Key Infrastructure, Quantum-Safe Migration, Transport Layer Security.
Development of Quantum Computers are growing rapidly, the security of today’s cryptographic systems which are working with Public Key Infrastructure (PKI) is at serious risk. RSA and ECC algorithms are the backbone of secure communication and digital identity can be breakable by quantum algorithms such as Shor’s. Hence, a transition is required to Post-Quantum Cryptography (PQC), which is designed to handle quantum attacks. This work provides a detailed review of how PQC can be integrated with the existing PKI, with a special focus on the auto-enrollment process. Auto-enrollment is an essential process but often overlooked mechanism, responsible for automatically issuing and renewing digital certificates. First, we explored how current PKI systems are exposed to the quantum threats and the readiness. The performance of the algorithms that are standardized by NIST, such as Kyber and Dilithium were discussed. We analyze the technical and operational challenges of transitioning to PQC by referencing both research studies and real-world implementations from major industry players such as Google and Microsoft. These include large key size, certificate size, compatibility issues, complex computations and need for crypto-agility. We also examine the hybrid approaches that combine classical and post-quantum methods as traditional strategies. The survey concludes by outlining best practices, deployment considerations, and open research challenges that must be addressed for a smooth, secure, and scalable shift to quantum-safe PKI. This work aims to guide researchers, engineers, and policymakers in building the next generation of cryptographic infrastructure that can stand the test-time even in a quantum world.
The impending threat posed by quantum-capable adversaries necessitates a secure and practical transition of Public Key Infrastructures (PKIs) to support post-quantum cryptography (PQC). This paper addresses the multifaceted challenges of integrating PQC into existing PKI ecosystems by examining novel cryptographic combiners and hybrid certificate designs that can provide quantum-resistant security. We assess the performance, compatibility, and security of these hybrid certificates across standard communication protocols such as TLS, considering variations in root and intermediate certification paths. In addition, we introduce key management procedures that cover signature generation, validation, and lifecycle considerations under both software and hardware constraints. Beyond X.509, alternative trust models and certificate mechanisms are also analyzed for specialized domains, including IoT, firmware signing, and smart cards.
In 1994, Peter Shor developed a quantum algorithm that can efficiently solve the factorization and discrete logarithm problems. These problems are the foundation of modern cryptographic algorithms and the existence of an efficient algorithm for solving them threatens their security. Although large-scale quantum computers capable of breaking current cryptographic algorithms are not yet available, advances in quantum technology and the risk of “store now, decrypt later” attacks make it essential to prepare for migration to quantum-safe cryptography today. For the past decade, the cryptographic community has been actively developing algorithms that are not exploitable by Shor’s algorithm; such algorithms are said to be “quantum-safe” or “post-quantum.” However, cryptographic algorithms do not exist in isolation—they are components of larger cryptographic systems, such as protocols or other cryptographic primitives. Migrating these systems to use quantum-safe algorithms is therefore a complex task. This thesis studies the migration of several widely used cryptographic systems to post-quantum cryptography. In particular, we consider the migration of the public-key infrastructure (PKI), the TLS protocol, the XML Encryption and XML Signature standards, the SAML security framework, the Advanced Electronic Signature (AdES) standard, and the password-authenticated public-key encryption (PAPKE) primitive. For each topic, we analyze how the presence of quantum adversaries affects the security of existing constructions and identify components that rely on cryptographic assumptions vulnerable to quantum attacks. Based on this analysis, we propose approaches for adapting these systems to use post-quantum cryptographic algorithms. The proposed solutions are considered in two main forms: purely post-quantum and hybrid post-quantum. Purely post-quantum approaches rely exclusively on post-quantum algorithms, while hybrid post-quantum approaches combine classical and post-quantum mechanisms in order to provide security as long as at least one of the underlying assumptions remains secure. Hybrid post-quantum approaches are primarily motivated by uncertainty regarding the security of post-quantum algorithms. For each proposal, we discuss the advantages and disadvantages of the design, including deployment complexity, compatibility with existing systems, and performance considerations. In several cases, we also provide proof-of-concept implementations and evaluate their performance through benchmarks. We study post-quantum public-key infrastructures, which form a fundamental component of many other cryptographic systems. We show that constructing a purely post-quantum PKI does not fundamentally differ from constructing a classical PKI. For hybrid deployments, we propose two approaches—the composite hybrid and the parallel hybrid—which differ primarily in their implementation complexity. We also survey and analyze existing proposals for post-quantum TLS. In contrast, systems such as XML encryption and XML signatures, the SAML security framework, and the eIDAS-related AdES standard have received little attention in the context of post-quantum migration. For these systems, we outline possible migration approaches and provide proof-of-concept implementations. In addition, we present an example migration plan for a Trust Service Provider that relies on all of the discussed cryptographic systems, together with the methodology used to develop it. Finally, we consider the migration of the cryptographic primitive PAPKE. We propose a novel construction that replaces an ideal cipher with a half-ideal cipher, resulting in more efficient quantum-safe constructions and motivating the study of a new public-key encryption property called decryption robustness.
The emergence of quantum computing introduces unprecedented risks to classical cryptographic schemes, particularly digital signatures that safeguard authentication, confidentiality, and data integrity across digital ecosystems. To address these concerns, this paper investigates the adoption of Post-Quantum Cryptography (PQC) within Public Key Infrastructure (PKI) frameworks, emphasizing its role in strengthening electronic signature (eSign) systems against quantum threats. Traditional PKI implementations rely on algorithms such as RSA and ECC in combination with Hardware Security Modules (HSMs) for secure key management; however, these methods are vulnerable to quantum algorithms like Shor's. We examine how quantum-resistant alternatives-including lattice-based, hash-based, and multivariate polynomial-based schemes standardized by NIST-can be integrated into PKI without compromising interoperability and compliance. A comparative evaluation highlights trade-offs in performance, storage, and computational complexity while demonstrating the feasibility of embedding PQC into existing eSign infrastructures. Our findings underscore the urgency of transitioning towards quantum-safe digital signatures to ensure resilience, regulatory alignment, and long-term trust in national-scale digital services.