The seal
Your seal is a personal mark you affix to your files. It does not prove your legal identity; it proves that one and the same mark, which only you can reproduce, recurs across a series of documents. A mark of trust: the more you use and claim it, the more value it holds.
Make your seal a mark of trust.
Three certainties, without entrusting us anything
DfinA never sees your file and does not know your identity. Nothing is sent. And yet, three things remain provable by anyone.
Integrity
The file is strictly identical, byte for byte, to the one that was certified.
Date
It existed at a given moment. On Premium, this date is engraved in the Bitcoin blockchain.
Origin
It bears your seal, a mark only you can reproduce.
Keep your seal phrase secret.
Affix your seal
At the moment of certification, in a few steps. Everything is computed on your device. Reserved for unlimited plans.
Certify your file
As usual. It never leaves your device.
Choose "Affix your seal"
The option appears once the file is certified.
Note your phrase
Seven words generated for you, plus a label if you wish.
Your mark is embedded
In the certificate and its QR code, next to the fingerprint.
Your seal phrase
Seven randomly drawn words. It alone reproduces your seal, identically, on any device.
There is no recovery. No one, not even DfinA, can retrieve or reset it. If you lose it, your already-affixed seals remain verifiable, but you will no longer be able to affix new ones under the same motif.
You may add a short label, up to six characters (for example perso, pro, photo): it further personalizes your motif and helps distinguish several seals. This label is added to the seven words, it never replaces them.
What is public, what stays secret
Your motif and its code form your seal. It's your visible signature: made to be displayed and recognized everywhere.
Your seal phrase. It alone reproduces the mark, and must never be shared.
Showing your motif and its code reveals nothing of your phrase: no one can guess it from this public information. That is what makes your seal displayable everywhere and, at the same time, impossible to counterfeit.
One seal, or several
From a single phrase, create several seals for different uses, giving each a short label.
A label such as perso, pro or photo produces a distinct motif and a different code. To others, these seals look independent: nothing links them. Only you know they come from the same phrase.
These seals share the same phrase. If you want truly compartmentalized identities, use a distinct phrase for each, with a dedicated subscription.
Getting your seal recognized
Affixing your seal is not enough: you also have to get it recognized. This rests on two moves.
Claim it publicly
Show your motif on your site, your profiles, your communications, like an artist displays their monogram. Your audience learns to recognize the files that bear your mark.
Prove you control it
On demand, thanks to the signature challenge. An impostor who has merely copied the image of your mark cannot meet the challenge.
The more you use and claim it, the more it becomes a mark of quality. It is entirely yours: no one can appropriate or reproduce it, not even DfinA.
The signature challenge
It proves, on the spot, that you hold the mark, without ever revealing your phrase.
A third party gives you an arbitrary challenge phrase, for example ciel-orange-42.
You sign it with your seal phrase, on your device.
You share a proof link. Anyone can verify that the holder of your mark signed this exact challenge.
When you are asked to prove, on the spot, that a given mark is yours, in case of doubt, dispute or plagiarism. At no point is your phrase revealed.
Verifying a seal
Two independent checks, which can be done separately or together.
Integrity
Does the file match its fingerprint? You compare the received file to the certificate's fingerprint.
The seal
Does the signature match the announced mark? This is verified from the link alone, without even having the file.
Neither of these checks reveals the seal phrase nor allows the mark to be reproduced.
Value and limits
The continuity of a body of work (one same mark across a series of pieces), the defense of authorship (a plagiarist cannot meet your challenge, and an earlier timestamp prevails), and a shield against impersonators.
Its legal value is relative: it is not irrefutable proof established by a bailiff, but an admissible element of evidence, subject to a court's assessment. It is not a qualified electronic signature under the eIDAS regulation. And a seal is worth nothing if you never claim it publicly.