Post-quantum migration: where to start? A 6-step guide

Migrating to post-quantum cryptography is not just a matter of “changing algorithms.” It affects applications, network equipment, cards and badges, PKIs, HSMs, connected devices and vendor contracts. French and European authorities agree on one message: start now, with a gradual approach. Here is a six-step process, inspired by recommendations from ANSSI (France's national cybersecurity agency).

1. Take a cryptographic inventory

You cannot migrate what you do not know. List where cryptography is used (protocols, applications, equipment, libraries), with which algorithms (RSA, ECDH, ECDSA…) and which key sizes. Network discovery tools and software dependency analysis help, but you will often have to ask vendors directly.

2. Rank assets by data lifetime

The key question: how long must this data remain confidential or authentic? Data that must stay secret beyond 2030 (health, defense, intellectual property, sensitive personal data) is already exposed today to the “harvest now, decrypt later” risk. This is the data to protect first.

3. Take the quick wins: TLS and SSH

Hybrid key exchange is already available in many software products. OpenSSH has used it by default since version 9.0, with ML-KEM (mlkem768x25519-sha256) since version 10.0, and TLS 1.3 has a standard (RFC 10024) for X25519MLKEM768. In February 2026, ANSSI published recommendations for the post-quantum transition of TLS 1.3, IPsec and SSHv2: use them as a basis for your configurations. Check that your servers, load balancers and proxies negotiate it: it is often a simple version or configuration update, with an immediate benefit against traffic harvesting.

4. Question your vendors

Ask each critical vendor for its post-quantum roadmap: planned algorithms, hybridization, timeline, compatibility with your equipment. Long-lived products (OT, networks, HSMs, endpoints) are the most sensitive, because they will still be in service when the threat materializes.

5. Build PQC into procurement and renewals

ANSSI considers it will be “unreasonable” to buy products without PQC after 2030. In practice, add a requirement for hybrid post-quantum support, or at least a credible roadmap, to your tender specifications now, and align the migration with natural renewal cycles.

6. Aim for crypto-agility

Standards will keep evolving: new backup algorithms, new parameter sets, possible weaknesses discovered. Design your systems so you can change algorithms without rebuilding everything: centralized configuration, up-to-date libraries, no hard-coded algorithms. ANSSI also published a paper on this topic in January 2026 (“ANSSI views on crypto agility”).

Mistakes to avoid

• Waiting for “the standards to be finished”: the main standards have been published since August 2024.
• Switching without hybridization: ANSSI strongly recommends combining a classical and a post-quantum algorithm.
• Forgetting signatures and certificates: this is the part that takes the longest to migrate.