The migration of remote-access and industrial communication systems from classical public-key cryptography to post-quantum cryptography (PQC) requires careful evaluation at both the protocol and system levels. This paper presents PQC-E2E-CA, a system-level evaluation framework for reviewing post-quantum and hybrid cryptographic configurations in Secure Shell (SSH). The framework integrates OQS-enabled OpenSSH and OpenSSL with Linux netem network emulation, automated experiment execution, SCP integrity verification, and statistical post-processing. The evaluation separates key exchange behavior from host key authentication. Specifically, it measures ML-KEM and hybrid ML-KEM as SSH key exchange mechanisms, and ML-DSA as a host-key signature mechanism. Experiments are conducted under controlled RTT and packet-loss conditions using a gateway virtualised client-server testbed. The results show that ML-KEM and hybrid ML-KEM can be integrated into SSH without prohibitive application-level session setup overhead in the evaluated environment. Among the evaluated configurations, ML-KEM-768 demonstrates comparatively lower SSH session establishment latency at 50 ms RTT with 0% packet loss. ML-DSA-44 achieves the lowest host-key authentication latency under the same conditions and maintains relatively stable performance at 150 ms RTT with 5% packet loss. SCP throughput results for 100 MB and 200 MB transfers indicate that sustained transfer performance is mainly influenced by RTT and transport-layer dynamics using a single dominant key exchange configuration. These findings support migration toward standardized post-quantum mechanisms in SSH-based gateway and remote-access environments, provided that algorithm choice and system configuration are validated under representative workloads and network conditions.
The migration of remote-access and industrial communication systems from classical public-key cryptography to post-quantum cryptography (PQC) requires careful evaluation at both the protocol and system levels. This paper presents PQC-E2E-CA, a system-level evaluation framework for reviewing post-quantum and hybrid cryptographic configurations in Secure Shell (SSH). The framework integrates OQS-enabled OpenSSH and OpenSSL with Linux netem network emulation, automated experiment execution, SCP integrity verification, and statistical post-processing. The evaluation separates key exchange behavior from host key authentication. Specifically, it measures ML-KEM and hybrid ML-KEM as SSH key exchange mechanisms, and ML-DSA as a host-key signature mechanism. Experiments are conducted under controlled RTT and packet-loss conditions using a gateway virtualised client-server testbed. The results show that ML-KEM and hybrid ML-KEM can be integrated into SSH without prohibitive application-level session setup overhead in the evaluated environment. Among the evaluated configurations, ML-KEM-768 demonstrates comparatively lower SSH session establishment latency at 50 ms RTT with 0% packet loss. ML-DSA-44 achieves the lowest host-key authentication latency under the same conditions and maintains relatively stable performance at 150 ms RTT with 5% packet loss. SCP throughput results for 100 MB and 200 MB transfers indicate that sustained transfer performance is mainly influenced by RTT and transport-layer dynamics using a single dominant key exchange configuration. These findings support migration toward standardized post-quantum mechanisms in SSH-based gateway and remote-access environments, provided that algorithm choice and system configuration are validated under representative workloads and network conditions.
The transition to post-quantum cryptography is reshaping the Secure Shell (SSH) protocol for remote administration. Post-quantum key exchange has been deployed in OpenSSH and is being standardized, while SSH authentication largely remains a signature-replacement effort. This path preserves the familiar public-key credential model, but inherits the size and computation overhead of post-quantum signatures, which can increase latency, traffic, and server-side load. KEM-based authentication offers a natural alternative to this signature-centric path, and SSH makes this especially attractive at the user-authentication layer, which is method-extensible, separated from transport-layer key exchange and host-key authentication, and already protected by the established channel. We present a drop-in KEM-based user-authentication method for SSH that replaces client public-key signatures with a session-bound challenge-response proof. The method fits into SSH's existing user-authentication framework, preserving the public-key credential model and enabling incremental deployment alongside existing methods. We provide a reduction-based security argument in the post-quantum ACCE framework, implement the design in OpenSSH using liboqs, and evaluate it under representative RTTs, TCP initial-window settings, and post-quantum migration configurations. Our results show that KEM-based authentication is competitive with compact signature-based authentication under representative network settings, while reducing median handshake latency by up to about 10% against large-signature hybrid baselines. The advantages are clearer when post-quantum signatures stress transmission or computation: median latency under small TCP initial windows falls by up to 7.3% versus ML-DSA and 17.9% versus SLH-DSA, while server-side online cryptographic cost is 59.1% lower than that for ML-DSA in the same NIST category.
Quantum computing poses a critical threat to classical public-key cryptography, driving the adoption of post-quantum cryptography (PQC).While PQC performance has been extensively benchmarked in TLS, empirical studies on the Secure Shell (SSH) protocol remain limited.This paper evaluates the integration of PQC and hybrid (classical+PQC) mechanisms into SSH using an OQS-OpenSSH 8.9 prototype with liboqs support.We measured handshake latency, session size, and Secure Copy Protocol (SCP) transfer performance across standardized algorithms (CRYSTALS-Kyber, CRYSTALS Dilithium, Sphincs+), Falcon, and hybrid configurations.Experiments on heterogeneous legacy hardware under realistic LAN conditions were validated through Wireshark captures and protocol checklists.The results show that Falcon yields the smallest handshake sizes, Dilithium offers balanced and stable performance, Kyber scales predictably with NIST security levels, and Sphincs+ incurs significant overhead.Hybrid modes add limited cost while retaining classical trust anchors.These findings extend SSH PQC research beyond handshake analysis, offering deployment-oriented guidance for quantum-safe migration.
This thesis investigates the current state of Post-quantum cryptography (PQC) in the industry, with a particular focus on its practical deployment, integration challenges, and performance implications.The study combines a structured analysis of academic literature, standardization efforts, and industry guidance with an experimental evaluation of PQC integration in widely used security protocols. The analysis shows that, while significant progress has been made in the standardization of quantum-resistant algorithms such as ML-KEM, ML-DSA, and SLH-DSA, real-world adoption remains in an early and transitional phase. Organizations primarily focus on evaluation and pilot implementations, as deployment is constrained by interoperability issues, implementation maturity, and the complexity of migrating existing cryptographic infrastructures.To complement the conceptual analysis, experimental measurements were conducted for TLS, SSH, and IPsec to evaluate the performance impact of hybrid post-quantum cryptographic mechanisms. The results indicate that performance overhead is not uniform across components. In particular, post-quantum signature schemes introduce significant computational and network overhead, mainly due to increased key and certificate sizes. In contrast, hybrid key exchange mechanisms show only moderate performance impact across all evaluated protocols.The findings highlight that the primary challenge of PQC adoption lies not in algorithm design but in practical integration and large-scale migration. Hybrid cryptographic approaches emerge as the most viable strategy for enabling a gradual transition, balancing improved security against quantum threats with operational feasibility.Overall, this thesis demonstrates that PQC is transitioning from a theoretical research field to a practical engineering challenge, with significant implications for the future design of secure communication systems.
The emergence of fault-tolerant quantum computing poses an existential threat to classical public-key cryptographic systems, including RSA and Elliptic Curve Cryptography (ECC), through Shor's polynomial-time factorization algorithm. The Harvest Now, Decrypt Later (HNDL) attack paradigm further amplifies this threat by enabling adversaries to archive ciphertext today for future quantum-enabled decryption, rendering long-term data confidentiality immediately at risk. While the National Institute of Standards and Technology (NIST) finalized post-quantum cryptographic standards ML-KEM (FIPS 203) and ML-DSA (FIPS 204) in August 2024, their practical integration into complete application-level communication systems remains a largely unaddressed research gap. This paper presents QuantumShield, a hybrid post-quantum secure peer-to-peer communication platform that integrates ML-KEM-768 for quantum-safe key encapsulation, ML-DSA-65 for authenticated digital signatures, and AES-256-GCM for high-throughput symmetric encryption. Our primary research contribution is a rigorous empirical analysis of PQC integration overhead in a real-world communication pipeline, quantifying latency, key size, and security trade-offs against classical RSA-2048 and ECC-256 baselines under controlled experimental conditions. Experimental evaluation across 1,000 iterations demonstrates that ML-KEM-768 encapsulation completes in 2.8 ± 0.2 ms compared to 4.1 ± 0.3 ms for ECDH key agreement — a 32% latency reduction while providing NIST Level 3 post-quantum security. The complete secure transfer pipeline processes 1 MB files in under 22 ms on commodity hardware. The system further provides interactive cryptographic visualization, adversary threat modeling, tamper detection simulation, and a hybrid migration framework demonstrating practical transition from classical to post-quantum infrastructure. QuantumShield establishes that quantum-safe communication is not merely theoretical but deployable today with negligible performance compromise.
The prospect of a cryptographically relevant quantum computer (CRQC) undermines the public-key primitives that secure virtually every layer of modern communication networks, from subscriber authentication in cellular cores to transport-layer key exchange. Adversaries already following a harvest-now, decrypt-later (HNDL) strategy make this threat actionable today for any traffic whose confidentiality must outlast a decade. Following NIST’s finalisation of the first post-quantum cryptography (PQC) standards, ML-KEM (FIPS 203), ML-DSA (FIPS 204), and SLH-DSA (FIPS 205) in August 2024, and the selection of HQC as a fourth key-encapsulation candidate in March 2025, research has shifted from algorithm design to network-level integration. This paper reports a PRISMA-2020-compliant systematic literature review of PQC migration in communication networks, structured around five research questions covering protocol and scenario coverage, quantitative performance impact, hybrid cryptography strategies, transition barriers, and open research gaps. Six databases (IEEE Xplore, Scopus, Web of Science, ACM Digital Library, SpringerLink, and MDPI) were searched (3229 records identified); after deduplication, title-keyword screening, full-text eligibility assessment, and a pre-specified quality appraisal (Q1–Q6, threshold ≥3/6) applied to 310 eligible studies, a final synthesis corpus of 141 studies (68 journal articles, 68 conference papers, 4 conference-derived book chapters, 1 workshop paper) was screened, quality-appraised, and synthesised narratively with supporting evidence tables. The review finds that transport-layer protocols (TLS 1.3, QUIC, DTLS 1.3) dominate the literature, that lattice-based ML-KEM/ML-DSA offer the most favourable latency–bandwidth–energy trade-off among standardised families, and that classical–PQC hybrid schemes are the de facto transition strategy across 5G/6G, IoT, VPN, and automotive scenarios, at the cost of 10–100× larger keys/signatures and 8–40% handshake latency overhead. Persistent barriers include constrained-device resource limits, immature hardware acceleration, incomplete IETF/3GPP standardisation, and public-key-infrastructure scaling. We propose a five-level PQC transition-readiness maturity model and identify large-scale field validation, PQC–QKD integration, and lightweight signature schemes as priority directions for future work.
Abstract—The advent of fault-tolerant Cryptanalytically Relevant Quantum Computers (CRQCs) presents an existential threat to modern information security. Shor's polynomial-time quantum algorithm renders widely deployed public-key cryptographic primitives—including RSA, Diffie-Hellman (DH), and Elliptic Curve Cryptography (ECDH/ECDSA)—completely vulnerable to private key derivation. Furthermore, 'Harvest Now, Decrypt Later' (HNDL) adversarial campaigns actively intercept and store encrypted enterprise telemetry today, anticipating future quantum decryption capabilities. In response, the National Institute of Standards and Technology (NIST) finalized its primary Post-Quantum Cryptography (PQC) standards in FIPS 203 (ML-KEM), FIPS 204 (ML-DSA), and FIPS 205 (SLH-DSA). However, transitioning complex enterprise IT ecosystems to quantum-resistant primitives introduces severe architectural and computational disruptions: public key and signature sizes increase by several orders of magnitude, cryptographic handshake latencies escalate, network packets experience Maximum Transmission Unit (MTU) fragmentation, and legacy Hardware Security Modules (HSMs) lack microarchitectural support for lattice-based polynomial arithmetic. This paper provides an exhaustive, mathematically grounded technical survey and architectural roadmap for enterprise PQC migration. We formalize the Module Learning with Errors (M-LWE) and Module Short Integer Solution (M-SIS) hardness foundations, evaluate hybrid classical/post-quantum cryptographic transition models across standard transport protocols (TLS 1.3, IKEv2/IPsec, SSH), and formulate an enterprise Crypto-Agility Maturity Model. Furthermore, we construct an empirical enterprise testbed measuring throughput, connection establishment latency, memory footprints, and packet fragmentation across legacy and quantum-resistant suites. Our results show that while ML-KEM-768 achieves microsecond-level encapsulation, its 1,088-byte ciphertext expands TLS ClientHello payloads into multiple TCP segments under constrained networks. Finally, we establish open research directions in post-quantum identity federations, stateful hash signature tracking, and hardware-accelerated polynomial arithmetic. Index Terms—Post-Quantum Cryptography (PQC), FIPS 203 (ML-KEM), FIPS 204 (ML-DSA), Crypto-Agility, TLS 1.3, Lattice-Based Cryptography, Harvest Now Decrypt Later, Hardware Security Modules (HSM), Enterprise Migration.