Word against word You say you sent it in March. They say they had it before. Without a date that depends on neither of you, there is no conversation.
The dated proof wins The exact file you sent, sealed before you sent it. Nobody can say you made it after seeing theirs.
Cents against lawyers Sealing at the moment costs cents; today, nothing. Arguing over authorship afterwards costs lawyers, months and, more often than not, the case.
The scene
“What a coincidence. We already had that in development.”
You sent the proposal in March: the concept, the mock-up, three pages of script. They said it was interesting and they would get back to you. They didn’t.
In October you see it. The campaign, the series, the app. Not identical, but it is yours under another name. You write to them, carefully.
“What a coincidence. We have had that in development since last year.”
You open your folder. You have the file, of course. But the date on the file is set by your computer, and the email you sent lives on their server, not yours. Your word against theirs.
The ritual: before you share, send or publish
- Close the version you are going to show: the PDF, the script, the mock-up, the pitch, the design, the zipped repository. The exact version, not “more or less that one”.
- Seal it before you hit send. Not after the meeting, not when you remember: before. The date on the seal has to be earlier than anyone else seeing it.
- Send or present that same version, untouched. If you change a comma after sealing, it is no longer the same file. If you put out an important new version, seal that too.
- Keep the exact file and the verification ZIP next to the email or message you sent it with. The three together tell the whole story: what you had, since when, and who you showed it to.
- Do it with everything you show before signing: proposals, synopses, chapters, demos, logos, prompts, decks. A ten-second gesture that replaces the sealed envelope.
What Sellat proves in this dispute
Sellat does not decide who the author is, who owns the work or whether one work copies another. That is for an agreement, a copyright registry or a judge.
Sellat proves one concrete thing: that the exact file existed on the date you sealed it, and that nobody has modified it since. It is technical evidence about an exact version of a file. It does not replace copyright registration: it complements it by fixing since when what you sent has existed. With it, “I had it first” stops being just your word.
What you keep after sealing
When you seal, you receive a PDF certificate and a verification ZIP by email. That ZIP is what you show when someone says they had it first: it contains the fingerprint of the exact file, the date and the instructions for anyone to check it without trusting you or Sellat. Sellat does not keep your work or publish it: nobody can read it from the proof.
The poor man’s copyright, but verifiable
The legend says all you need is to mail yourself a sealed envelope by registered post and never open it. The problem is that an envelope can be steamed open, resealed and posted again, and that you are the only one who says what was inside.
Sealing is the version of that idea that survives scrutiny. The date is fixed by a public reference that neither you nor Sellat can alter, and the proof refers to an exact file: if anyone changes a single letter, it no longer matches. No notary, no envelope, no waiting for the postman.
Open the package Close the package
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original/<archivo> If the original is kept
Your file, byte for byte
The exact photo you sealed, in a folder of its own so no other file in the package can be mistaken for it. It travels inside when the original is available: the upload that created the proof, or custody.
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certificado-<id>.pdf Always
The readable certificate
The PDF you show a person or attach to a filing. It is an informative document: what actually gets checked is the file, not the PDF. If the file carried Content Credentials (C2PA), the certificate records them too — who signed, with which tool and whether they declare AI use — exactly as your browser read them when you protected it.
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proof.json Once the batch is anchored
The portable proof
Your file fingerprint, its Merkle leaf and inclusion path, the batch root and the public transaction that records it. This is the piece that lets anyone check everything without Sellat.
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sello-cualificado-<id>.tsr With a qualified seal
The qualified seal
The RFC 3161 response from the qualified timestamping authority, exactly as it was issued. This is the file that fixes the date under eIDAS.
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autoridad-sellado.pem With a qualified seal
Who signed the seal
That authority signing certificate, with its SHA-256 written into the README. It travels inside so the check works offline and nobody has to go looking for it.
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anclaje-bitcoin.ots Once the batch is anchored
The Bitcoin anchor
The OpenTimestamps proof of the batch root. It may still be waiting for a block: it is a valid file and whoever receives it can upgrade it themselves.
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LEEME.txt / README.txt Always
The instructions, in two languages
What each file is, what it proves and what it does not, and the exact commands to check it. In Spanish and English, so an expert or a lawyer never has to ask you anything.
The seal is signed by FNMT-RCM, not by Sellat.
Sellat is not the party attesting the time. The qualified seal is issued by a qualified timestamping authority of the FNMT-RCM, and its signing certificate travels inside your package. We are the intermediary that joins your fingerprint to that seal and hands it to you in a tidy folder.
It checks out without us and without the internet.
With the seal and the authority certificate inside the ZIP, the date is verified with standard tools on the machine of whoever receives it. If Sellat disappeared tomorrow, your package would still check out.
Seal the version before you send it. Ten seconds.
Sealing at the moment costs cents; today, nothing. Arguing over authorship afterwards costs lawyers. Upload the exact file you are about to show and keep the certificate next to the email you send it with.
Seal before sending 
