The Cryptographic Inventory, Where to Start

Every post-quantum guide starts with the same step. ANSSI advises public and private organizations to start an inventory now. NIST's migration project calls finding where public-key cryptography is used "the first step in PQC migration planning". The British NCSC asks for a full discovery exercise by 2028. Then the guides leave you alone with a spreadsheet.

Here is how to make that spreadsheet useful, starting from what ANSSI expects it to contain.

What ANSSI expects

In its post-quantum FAQ, ANSSI asks every organization for an inventory of the products and business uses that include cryptography, the algorithms they use, and the data whose confidentiality or authenticity must be guaranteed after 2030, with that duration stated every time.

Three columns, then. Where, with what, and for how long. The third one turns a list into a plan.

Start from the data

An inventory that starts from the infrastructure lists thousands of TLS certificates and drowns in them. Start from the data that must stay secret or provable for years, and follow it.

• Archives and backups. What is encrypted, with which key, and how long it is kept.
• Documents exchanged with partners. Contracts, medical or financial files, industrial plans, sent by e-mail or file transfer.
• Signatures that must hold. Signed contracts, invoices, evidence, software releases.
• Data inside applications. Encrypted database fields, tokens, files encrypted by the code itself.

For each one, write down how long it must stay protected. A record kept 30 years and encrypted today with RSA is exposed to "harvest now, decrypt later" from today.

Then the systems

• Network protocols. TLS, SSH, IPsec and VPNs. A discovery tool scanning the network finds most of them.
• Code and pipelines. The cryptographic libraries the applications call, and the keys and certificates in the build and deployment pipelines.
• The products you buy. Discovery tools may miss the cryptography embedded in products, as the CISA, NSA and NIST factsheet of August 2023 warns. Ask each vendor for the list, and for its post-quantum roadmap.
• Keys and certificates. Where they are stored, who owns them, when they expire.

To keep the result in a standard format, CycloneDX 1.6 defines a Cryptography Bill of Materials (CBOM), a structured way to describe cryptographic assets that tools can exchange.

Then the order

Cross the two lists to rank the work. The European roadmap of June 2025 asks for high-risk uses to move by the end of 2030 at the latest.

• First. Long-lived confidential data encrypted with RSA or elliptic curves. It is what harvest now, decrypt later targets, and the simplest to protect, because it goes through a file or message format.
• Next. Exposed protocols, TLS first. Updating OpenSSL and the servers often brings a hybrid key exchange with it.
• Then. Long-lived signatures, certificates and the public key infrastructure, whose post-quantum standards are still being completed.
• Last. Data whose confidentiality ends within a few years, which harvest now, decrypt later threatens least.

An inventory without durations is a list. With them, it is a migration plan.

Keep it alive

An inventory is out of date the day a new application ships. Give each line an owner, review it at fixed intervals, as NIS2 and DORA already ask of the cryptographic policy, and add the algorithm question to every new project and every purchase.

Where Feranor PQC Suite fits

Once the inventory shows long-lived files and messages encrypted with RSA or ECDH, Feranor PQC Suite protects them. Its command line re-encrypts classical archives, from OpenSSL, S/MIME or .NET, to hybrid post-quantum recipients, in batches with a journal. Its messages are standard CMS, and fpqc inspect shows which algorithms each one uses, which makes the next inventory easier.