Sellat

Sellat creates independently verifiable proof that an exact file existed at a given moment. Ask to protect a file and a Sellat panel opens in the conversation: your browser computes the file's SHA-256 fingerprint, and only that fingerprint and the file name reach Sellat. The file never leaves your device. Sellat anchors the fingerprint on the public Polygon blockchain in a Merkle batch and attests it on Bitcoin through OpenTimestamps, so anyone can verify the proof later without trusting Sellat.

You can also add a qualified electronic timestamp from FNMT-RCM (eIDAS, RFC 3161) to a proof. It uses one of the qualified seals available in your Sellat account and is only requested when you ask for it.

From here you can:

• Protect a file, or a SHA-256 fingerprint you already have.
• Check the status of a proof: Polygon anchor, Bitcoin confirmation, qualified seal and certificate link.
• List your proofs.
• See your plan, today's budget and the qualified seals you have left.
• Add the FNMT-RCM qualified timestamp to a proof.

Built for freelancers, creators, small businesses and anyone who needs evidence that a document, photo, contract or design existed in a given state at a given time.

Limits: a proof shows that those exact bytes existed no later than the anchored time; on its own it does not prove authorship or ownership. Proofs are anchored in batches, and each proof tells you when its batch is anchored. Files kept in custody, billing and account settings stay in the Sellat dashboard, out of reach of the plugin. It needs a Sellat account. You choose what it may do on the consent screen, the qualified seal is a separate permission, and you can disconnect it at any time from your Sellat dashboard.