Post-Quantum Cryptography: Standardisation, Algorithms, and Deployment Migration

Abstract

The prospect of cryptographically relevant quantum computers threatens public-key primitives underpinning modern digital infrastructure, including RSA, Diffie-Hellman, and elliptic-curve cryptography. Post-quantum cryptography (PQC) responds with algorithms believed to be hard for both classical and quantum adversaries. In August 2024, the U.S. National Institute of Standards and Technology (NIST) finalised the first three PQC standards: FIPS 203 (ML-KEM, based on Kyber), FIPS 204 (ML-DSA, based on Dilithium), and FIPS 205 (SLH-DSA, based on SPHINCS+). This paper surveys the algorithmic families behind these standards, the harvest-now-decrypt-later threat model, hybrid migration strategies, performance trade-offs, and the engineering challenges of transitioning the global cryptographic stack. We examine deployment progress in TLS, SSH, X.509, and constrained devices, and outline open research questions on side-channel security, falcon-style signatures, and the long-term replacement schedule for classical asymmetric cryptography.