Certify What? When? Who?
We turn your file into a unique fingerprint, then we anchor it. Three questions, three answers: the same file, on this date, by this entity. All without ever sharing your file.
The three anchors
To anchor is to fix a fact so it can no longer be denied. DfinA fixes three of them around your file.
The SHA-256 fingerprint, computed in your browser, proves the file is the same, byte for byte. It never leaves your device.
A timestamp attests that the file existed at that instant. Certified by DfinA, and, on Premium, engraved in the Bitcoin blockchain.
The seal proves that one and the same entity, recognizable by its mark, is behind the file. A motif only you can reproduce.
A proof in a few steps
Simple, fast, and designed so you keep control of your files.
Drop a file
Image, audio, video, document. It stays on your device.
The fingerprint is computed
Locally, in your browser. Only 64 characters come out: the "what".
Date, and a seal if you wish
The fingerprint gets a DfinA date and a certificate. On Premium it is anchored in the Bitcoin blockchain; unlimited plans can affix their seal.
Verify at any time
By QR code or with open tools, without depending on us.
Three anchors, two strengths
Each anchor has a baseline, and can be reinforced. Content and date are guaranteed for everyone; the entity is added optionally.
| Anchor | Baseline | Reinforcement |
|---|---|---|
| The content | SHA-256 fingerprint all plans | Absolute by nature: a fingerprint matches, or it does not. |
| The moment | DfinA timestamp all plans | Engraved in the Bitcoin blockchain Premium |
| The entity | Optional | Attributable seal unlimited plans |
A file without a seal is already fully certified on content and date. The seal adds the "who": an inimitable mark you affix and that anyone can recognize, without ever revealing your secret.
Why the Bitcoin blockchain?
The Premium plan engraves your date on the blockchain. A proof is only valuable if no one can alter it.
All certificates already carry a DfinA date. The Premium plan adds a date engraved on the Bitcoin blockchain, verifiable by anyone, without depending on us.
We chose the world's most secure and resilient blockchain to anchor document fingerprints: a public, decentralized ledger independent of any company or institution.
Your document is never published there. Only its cryptographic fingerprint is recorded, to establish its existence at a given date.
The Bitcoin blockchain is thus used here as a proof infrastructure. For you, the service works simply, with a fixed price and payment in your usual currency.
What we do, and what we don't
We provide a technical timestamping and proof-of-existence service for a digital fingerprint at a given date, independently verifiable.
Verification demonstrates that a document existed at a precise date and that the content presented today matches exactly the one that was timestamped.
We store no file, do not verify content, certify neither legality nor intellectual property, and replace neither a notary, nor a lawyer, nor a public authority. The user remains solely responsible for the content matching the fingerprint.
The seal attests a continuity of origin, not a legal identity: it does not replace a qualified electronic signature.
Ready to anchor your files?
Computation is local, the file never leaves your device, and the certificate is verifiable at any time.
Certify a file