Iranian Society of Cryptology The ISC International Journal of Information Security 2008-2045 18 3 2026 07 01 Recent Trends in Post-Quantum Cryptography Integration and Performance in the Internet Security Stack 155 166 241265 10.22042/isecure.2026.241265 EN Togu Novriansyah Turnip Department of Engineering Technology, Technical University of Denmark, Denmark Faculty of Vocational, Del Institute of Technology, Indonesia Birger Andersen Department of Engineering Technology, Technical University of Denmark, Denmark Cesar Vargas-Rosales Tecnologico de Monterrey, School of Engineering and Science, Monterrey, Mexico Journal Article The rapid advancement of quantum computing poses a direct threat to classical public-key cryptographic systems at the core of Internet security protocols. Post-quantum cryptography (PQC) has therefore become central to ongoing standardisation and early deployment efforts. This paper presents a comparative analysis of PQC integration into TLS, SSH, and IPsec, examining cross-cutting challenges, protocol-specific trade-offs, and deployment considerations. Our findings show that PQC adoption introduces markedly uneven overheads across protocols: handshake latency may increase by up to 600% in TLS, by 29% in SSH, and by up to 300% in IPsec, while memory requirements in hybrid configurations can exceed 300 KB in resource-constrained environments. We further demonstrate that message fragmentation, certificate chain expansion, and cumulative rekeying costs emerge as protocol-dependent bottlenecks, underscoring that migration strategies must be tailored to the architecture and operational context of each protocol. Beyond performance, we identify interoperability gaps, downgrade vulnerabilities, and side-channel risks as critical obstacles to secure deployment. By combining empirical performance evidence with a structured review of challenges and deployment strategies, our study provides actionable insights for practitioners, informs ongoing standards development, and highlights research priorities essential to building a resilient, quantum-resistant Internet infrastructure. https://www.isecure-journal.com/article_241265_02b9c0d1798080db6682db28db5e53fb.pdf