Post-quantum cryptography (PQC)
PQC · quantum-safe cryptography · quantum-resistant cryptography · ML-KEM · ML-DSA · SLH-DSA · harvest now, decrypt later · cryptographie post-quantique
New encryption and signature algorithms designed to withstand a future quantum computer capable of breaking RSA and the elliptic curves that protect the internet today.
In practice
NIST published the first three standards in August 2024: FIPS 203 (ML-KEM, key establishment), FIPS 204 (ML-DSA, signatures) and FIPS 205 (SLH-DSA, hash-based signatures). The urgency comes from “harvest now, decrypt later”: an adversary can record encrypted traffic today and decrypt it once the machine exists. ANSSI, the French national cybersecurity agency, insists on hybridisation, which pairs a post-quantum algorithm with a proven classical one, and considers it unreasonable to buy products without post-quantum cryptography after 2030. The EU’s coordinated roadmap of June 2025 targets migration of high-risk use cases by the end of 2030.
Fictional case: a law firm archives correspondence that must stay confidential for thirty years. Its cryptographic inventory shows that these exchanges rely on RSA, so those flows move to the top of its migration to hybrid key exchange.
How to protect yourself
- Inventory your cryptographic uses: protocols, certificates, libraries, hardware.
- Prioritise data that must stay confidential for more than ten years.
- Ask suppliers for a post-quantum roadmap, hybrid first.
