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24 October 2026 · Updated at 07:47 GMT FR EN ES Member area Log in
Certification

Blockchain

How a certificate's fingerprint is calculated, recorded on a distributed ledger operated by OIMAP and then anchored and time-stamped on a public blockchain.

Updated : October 28, 2026· 3 min read

A technology in the service of proof

Seal with Two Qilin Playing (1849)
Seal with Two Qilin Playing (1849)

Blockchain is not an end in itself here. It serves one precise purpose: guaranteeing that a certificate has not been altered since the day it was issued.

This page describes the architecture in accessible terms: what is calculated, where it is recorded, who can verify and what guarantees result.

The technical choices favour sobriety: little data on the chain, no personal data, and an architecture deliberately simple to audit.

  • Fingerprint
  • Permissioned ledger
  • Public anchoring

The architecture in figures

2layers: OIMAP ledger and public chain
256bits of fingerprint
0personal data on the chain
< 10 minfor a time stamp

From certificate to anchoring

  1. Fingerprint

    An algorithm calculates a 256-bit fingerprint of the certificate and its file.

  2. OIMAP Registry

    The fingerprint is recorded on a permissioned distributed ledger, kept by OIMAP and its Member States.

  3. Grouping

    The day's fingerprints are grouped in a cryptographic tree.

  4. Anchoring

    The root of the tree is published on a public blockchain.

  5. Time-stamping

    The date of publication proves that the fingerprint existed at that moment.

Why two layers?

A permissioned ledger makes it possible to control who writes: only OIMAP can record a fingerprint. A public blockchain allows anyone to verify that this record exists, without depending on OIMAP.

The combination brings the discipline of one and the neutrality of the other: no one, not even OIMAP, can backdate or alter a fingerprint that has already been anchored.

Jar with Design in Underglaze Iron (1800s–1900s)
Jar with Design in Underglaze Iron (1800s–1900s)
Turtleback Reading Lamp, Tiffany Glass & Decorating Company (c. 1895–1902)
Turtleback Reading Lamp, Tiffany Glass & Decorating Company (c. 1895–1902)
Mirror with Concentric Circles, an Immortal, and Auspicious Animals (100 BCE–100 CE)
Mirror with Concentric Circles, an Immortal, and Auspicious Animals (100 BCE–100 CE)

OIMAP ledger or public blockchain

Carved Lacquer Scroll Box (1736–95)

OIMAP Registry

Permissioned
  • Written only by OIMAP
  • Data associated with the file
  • Consultable by professionals

Keeps control and confidentiality.

Lampas with foliate medallions in ogival lattice (1400s)

Public blockchain

Open
  • Readable by all
  • Contains only the root of the tree
  • Impossible to rewrite

Guarantees the date and neutrality.

No personal data

What is stored, and where

Distribution of data
DataOIMAP RegistryPublic chain
Certificate fingerprintYesVia the root of the tree
OIMAP numberYesNo
Owner's nameNo (kept in the Registry)No
File and documentsNo (kept in the Registry)No
Date of entryYesYes

Security: measures in place

Write-access control95
Logging of operations90
Node redundancy85
Annual external audit80

Internal maturity index, out of 100 (indicative).

The technical choices

  1. Permissioned ledger

    Choice of a controlled ledger for writes.

  2. Public anchoring

    Daily publication of the root.

  3. Audit

    First independent audit of the architecture.

  4. States' nodes

    Member States host verification nodes.

Case study: detecting a forgery

An altered certificate

Situation

A certificate is doctored to change a dimension. A buyer has it checked.

Actions
  1. The file received is submitted to the verification page.
  2. The recalculated fingerprint differs from the anchored one.
  3. The page displays “document altered”.
Outcome

The forgery is exposed in a few seconds, without any intervention by OIMAP.

Jar with Stamped Decoration (1400s)
Jar with Stamped Decoration (1400s)
Daffodil Table Lamp, Tiffany Studios (c. 1910–13)
Daffodil Table Lamp, Tiffany Studios (c. 1910–13)
Teapot with Landscape and Imperial Poem, Chen Hanwen (1762–95)
Teapot with Landscape and Imperial Poem, Chen Hanwen (1762–95)

Good practices

An engineering principle

Arion on a Sea Horse and Bacchante on a Panther (pair), William Adolphe Bouguereau (1855)
« The simpler a system is, the easier it is to audit, and so to trust. »
Technical team, OIMAP

Technical vocabulary

Hash
Digital fingerprint of a file.
Merkle tree
Structure that groups many fingerprints into a single root.
Node
Computer taking part in the verification of a ledger.
Anchoring
Publication of a fingerprint on a public chain.

Frequently asked questions

Does blockchain consume a lot of energy?

Anchoring is published only once a day; the energy footprint is negligible.

What happens if the public chain disappears?

The OIMAP ledger keeps the fingerprints and the anchoring proofs; a new anchor is published on another chain.

Who can verify?

Everyone, thanks to the verification service.

Can OIMAP modify a fingerprint?

No: it can publish a new one (revocation, update), but never erase the old one.

Technical documents

Contacts

Egypt and Nubia, Volume I: The Great Temple of Aboo-Simble, Nubia, Louis Haghe (1846)
Egypt and Nubia, Volume I: The Great Temple of Aboo-Simble, Nubia, Louis Haghe (1846)
Certification DepartmentParis — Headquarters+33 1 00 00 00 00certification@oimap.exampleMonday to Friday, 9 a.m. – 5 p.m.

Verify a certificate

Annunciation to the Shepherds: Leaf from a Book of Hours (1 of 6 Excised Leaves), Henri d'Orquevaulx (c. 1420–30)

Check the fingerprint of a digital certificate right now.

Verify
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