Lea is an illustrator in Bern. She has just finished a new character design, and she wants to prove the date before she shows it to a client. She opens the sealing tool, then stops. Does her artwork leave her computer and travel to some outside company? The worry is fair. Here is exactly what the timestamp authority receives when she seals the file, and what never leaves her side.
The short answer
Only a fingerprint of your file goes to the timestamp authority, never the file itself.
When you seal a document, the platform does not send your file to the timestamp authority. It sends only a short code worked out from the file. That code is called a cryptographic hash. The timestamp provider for the platform is Swisscom Trust Services. It receives the hash and issues a qualified time stamp. Your artwork, your text and your images stay out of that exchange. So the idea that the timestamp authority receives hash only is not a slogan. It is what actually happens.
What a hash is
A hash is a short fingerprint of a file that cannot be turned back into the file.
A hash is a line of letters and numbers worked out from the content of a file. The same file always gives the same hash. Change one word or one pixel, and the hash changes completely. You cannot rebuild the file from the hash, in the same way you cannot rebuild a person from a fingerprint. That is why the hash can stand in for the file. It proves which file you mean without showing what the file says.
What the timestamp authority receives
Swisscom Trust Services gets only the hash, and returns a qualified time stamp under RFC 3161.
A timestamp authority is a trusted outside party. Its job is to record that a given hash existed at a given moment. When you seal a file, only the cryptographic hash, the fingerprint of your file, goes to Swisscom Trust Services, which issues a qualified time stamp under RFC 3161, the internet standard for time stamping. The authority adds the time and signs the hash and the time together. The file stays with you. Only the fingerprint makes the trip.
Why send only the hash
Sending the fingerprint, not the file, keeps your content out of the time stamp step.
There are two reasons the platform works this way. First, the timestamp authority does not need the file to do its job. It only needs something that stands for the file, and the hash does that. Second, the fingerprint is small and always the same length, so it is quick to send and simple to sign, whatever the file is. The result is the same either way. You get a signed record that your exact file existed at a given time, with the file itself kept out of the exchange.
Why the time can be trusted
The time comes from an audited clock, and eIDAS Article 41 presumes it is accurate.
The hash is signed together with a time taken from an audited clock. Under Article 41 of eIDAS, the European rules on electronic trust services, a qualified electronic time stamp carries a presumption of the accuracy of the date and time it shows. A presumption means a court starts from the position that the time is correct. Anyone who disputes it must bring evidence to argue otherwise. That is a strong starting point for a dated record.
What stays with you
Your file content is never part of what the timestamp authority sees.
Because only the hash travels, the timestamp authority never sees your characters, your words or your images. This matters for a draft you do not want to share yet, a design, a contract term or a private note. If you do want the platform to keep the file for you, Storage and Escrow are separate choices you can make. Those options are about holding the file, not about the time stamp step. You decide what to share and when. Even then, the timestamp authority still sees only the hash, and your content stays out of that step.
How to check it later
Anyone can confirm the time stamp through the public verification link, without an account.
When the seal is done, you get a certificate and a public verification link. Anyone you send the link to can open it, with no login, and see the hash and the time. If the file is changed by even one character, its hash no longer matches, and the check fails. That is how a reader knows the file is the same one you sealed. Note what the seal shows and what it does not. It shows which file was sealed and the moment it was sealed, not who wrote it. You can try a check yourself on the validator, and see the full flow on how it works.
Back to the illustrator
Lea can seal the design and keep the file to herself while still proving the date.
Lea seals her character design. The fingerprint goes to the timestamp authority, the signed time comes back, and her artwork never leaves her computer. She now has a dated record she can show, and the picture itself is still only hers to share. The lesson is simple. Seal it before you share it, and only a fingerprint leaves your hands. Start at swisstrustlayer.com.
