01
FRANCE TITRES / ANTS
2D-DOC
Format specifications, document profiles and trust resources for the French ecosystem.
Specifications & profilesRead the source← Secure developmentThe proof
VDS VERIFY / 2D-DOC / CEV
The proof
in the code.
A small printed square. Signed data. And expert engineering to read it, verify it and understand what it proves. With VDS Verify, Stelau makes that proof accessible.
A mobile app, an API and an SDK built by Stelau.
5 M+France Identité users
Stelau code. In everyday use.
Our SDK is integrated into France Identité. Our API is also used to generate its visible digital seals and in France Titres’ 2D-DOC verification service.
The figure refers to France Identité users, not a scan count. France Identité · 1 October 2026 · VDS Verify integrations
01 / What the code protects
A 2D-DOC is first
an electronic signature.
The code carries data and its signature. This signature makes it possible to check that the covered data has not been changed, and establish its origin within a defined trust framework. The QR code or Data Matrix carries that proof.
A visible digital seal (VDS, or CEV in French) bridges a document and a proof that a machine can verify.
STELAU / PROOF IN MOTION
Change the data. Break the proof.
Educational simulation · fictional data · non-scannable code
- 01Issue
The issuer signs the document’s data.
- 02Verify
The reader checks the signature of the received data.
- 03Modify
Data in the code changes; the signature stays the same.
- 04Detect
The signature no longer matches the modified data.
The signature covers the data in the code. Printed text must also be compared with that data.
02 / From standards to practice
Read the specifications.
Make the formats work.
Our work connects 2D-DOC specifications, standardised seals and documents already in circulation. A standard’s name never removes the need to specify the profile, version and trust conditions.
02
INTERNATIONAL STANDARD
ISO 22376:2023
A framework for the structure, representation, production and verification of visible digital seals.
Published in 2023Read the source03
LEGACY COMPATIBILITY
AFNOR XP Z42-105
A supported format for existing seals. The September 2020 standard has since been withdrawn.
Withdrawn standard / existing formatsRead the sourceISO 22376 does not, on its own, replace national specifications or trust governance rules. ISO 22376:2023
03 / Our verifier
See the data.
Understand the result.
VDS Verify reads codes on paper or on screen, displays decoded data and shows the verification result. Seal and certificate details take the result beyond a simple green indicator.
The app
A mobile reader for examining documents and signed data. Its code is published under Apache 2.0.
The API
Services for generating, decoding and verifying seals within your workflows.
The SDK
Integration within other applications, such as France Identité.
04 / Experts who code
Decoding
is not verification.
In the public app, the scanned code is sent to an API for decoding and verification. The app then checks the result’s structure before displaying it. This excerpt shows the boundary between reader and service; it does not show the cryptographic engine.
Behind this apparent simplicity lies the implementation work: handling data precisely, explaining errors and never confusing a successful read with a valid proof.
index.tsx / EXCERPTTS
const response = await integrityFetch(
apiUrl,
"/api/v1/decode",
JSON.stringify({ vds: b64encodedvds }),
);
const { success, message, vds } = await response
.json()
.catch(() => ({}));
if (success === true) {
const normalized = normalizeVdsResult(vds);
if (!normalized) {
showError("error_invalid_qr");
return;
}
// …
}Read the right bytes.
Encoding, headers, versions and schemas: verification applies to an exact representation of the data, not an approximation of the displayed text.
Establish trust.
A mathematically correct signature is not enough. The issuer’s certificate, its validity and applicable revocation information must be examined.
Support coexisting formats.
Distinguish seal families and document profiles; handle changes while preserving the ability to read documents already issued.
Explain the result accurately.
Decoded data, verified signature, indeterminate result: distinct states that the person making a decision can understand.
05 / Paper, copies and the holder
A proof that travels.
A scope to understand.
A seal can be printed and read again: if the code stays readable, its data and signature survive the change of medium. This ability to move back to paper is a practical benefit for today’s uses.
A static seal can also be copied. Its signature can remain valid without establishing that the presenter is its legitimate holder. Integrity and protection against unauthorised transfer are distinct questions.
STELAU / PROOF IN MOTION
The medium changes. The signature stays.
Educational simulation · fictional data · non-scannable code
- 01Display
A digital document carries signed data.
- 02Print
The same code moves to paper without changing its content.
- 03Read again
The reader retrieves the data and checks its signature.
- 04Distinguish
A copy can retain a valid signature without proving that the presenter is legitimate.
If the code stays readable, printing preserves the cryptographic proof. It does not establish who presents it.
Holder binding: another layer of proof.
Depending on the protocol and its implementation, a wallet can add proof of possession and bind a presentation to a verifier’s challenge. These mechanisms complement the document’s signature. Our work on nested seals also explores binding certified data to the presenting device.
Your next use case
A document to sign.
A proof to integrate.
Seal issuance, document reading, verifier integration: our experts support you from choosing the format to implementation, with a precise understanding of the guarantees required.
Let’s discuss your project