Post-Quantum Cryptography in Practice: A Critical Integrative Review of Implementation Assurance and Migration Readiness

Secure post-quantum migration requires evidence beyond algorithm standardisation. Thiscritical integrative review connects implementation assurance, system performance andmigration readiness using literature available through 19 September 2026 and a docu-mented supplementary search conducted on 6 November 2026 within that publicationwindow. Four analytical instruments distinguish mathematical assumptions, demonstratedcountermeasure scope, workload-dependent bottlenecks and organisational dependencies.Full-text comparisons show why pre-standard implementations, fixed classical authentica-tion and different timing boundaries prevent direct transfer of performance results. Threeinference risks organise the synthesis: treating exploit repair as vulnerability-class assur-ance, primitive efficiency as end-to-end feasibility, and hybrid key exchange as completereadiness. An illustrative walkthrough makes requirement-level decisions explicit withoutclaiming comparative validation. Specification-based examples quantify authenticationexpansion in TLS and screen all 15 FIPS 204/205 signature parameter sets against adeclared firmware profile. Two ML-DSA-65 certificates plus CertificateVerify require 13.8kB of raw cryptographic material; firmware eligibility changes with the category, sizebudget and permitted portfolio. Neither result establishes deployment suitability. Source-linked extraction records, decision rules and executable calculations support conditionalengineering decisions and a research agenda with measurable validation criteria. Theinstruments organise evidence; their predictive validity remains untested.