Timestamp a file without revealing it

The awkward part of proving you had something first is that proof usually means handing it over. You want a date on the draft, the design, the model weights — but you do not want to publish them, and you certainly do not want to email them to a company you just met.

You do not have to. You can seal the fingerprint instead.

What a fingerprint is

SHA-256 turns any file, of any size, into a fixed 64-character string. The same bytes always produce the same string. Change one comma and the string changes completely, in a way nobody can steer. And it only runs one way: from the string, the file cannot be reconstructed or guessed.

So the fingerprint is a perfect stand-in. It says nothing about your content, and it can only have come from your content.

Why sealing one proves existence

Registering a fingerprint on a dated, append-only record makes a narrow but very strong claim: these exact bytes existed at this moment. Nothing about who made them, and nothing about who owns them — but that one fact, provable at will, is what decides priority arguments.

Later you reveal the file only to whoever needs convincing. They recompute the fingerprint, compare it to the sealed record, and the date is either there or it is not. No trust in you required, and none in us.

Two independent witnesses

A notary that only vouches for itself is worth little, so each record carries two proofs that outlive us:

• RFC 3161 timestamp. The internet standard for trusted timestamps. An independent authority signs the fingerprint together with the time, and that signature verifies on its own — with our servers switched off.
• Bitcoin anchor. The record is committed into the Bitcoin blockchain. To move the date, someone would have to rewrite the most expensive ledger ever built.

On top of that the registry is append-only: entries are chained, so removing or reordering one breaks every entry after it, visibly and permanently.

What this does not do

It does not prove you are the author — only that the bytes existed. It does not register a copyright or a patent. It does not stop anyone copying your work; it makes the copy arguable. Those limits are real, and spelled out here.

The whole thing is one call. Send the digest to POST /api/certifications/hash and you get a permanent verification URL back. Agents can do it over MCP or A2A instead — see the skill manual. Free, no account, no key.