Proof, not trust.
A seal is proof carried by the file itself: a signature over every byte, anchored to the blockchain. Here's exactly how it's made, and how anyone can check it for free.
Fingerprint the whole file
We take a SHA-256 hash of the entire file, a 64-character fingerprint that changes completely if a single byte changes. This is what gets protected.
Seal it
A seal covers the whole file, chaining to a published root, as PAdES for PDFs, C2PA for images and media, XML-DSig for XML, S/MIME for email, or a detached CMS signature for any other file. Tamper with any covered byte afterward and the seal no longer matches.
Anchor it to the blockchain
The fingerprint is timestamped into the blockchain via OpenTimestamps, and recorded in a public, append-only transparency log. That gives independent, permanent proof the file existed at that moment.
Anyone verifies, keyless
To check a file, anyone re-hashes it and confirms the seal, the transparency-log entry, and the blockchain anchor, free and instant, open to everyone. If it matches, it's authentic and unchanged.
What tampering looks like
There are only two ways to change a sealed document, and both are caught:
Change the amount, a name, a date, anything covered by the signature, and the fingerprint no longer matches. Verification fails immediately.
Add pages, rewrite metadata, or append bytes (the way tools like exiftool do) and the signature no longer covers the whole file. We require full-file coverage, so this is flagged too.
A document only shows as authentic when it is byte-for-byte identical to what was sealed. Copying a visual badge onto a different file doesn’t work either. You verify the file, not a picture of a seal.
What a seal proves
- The document existed at a specific time, anchored to the blockchain.
- It hasn’t changed by a single byte since.
- Every document from the same issuer traces to the same seal.
A seal proves the document, its integrity and its moment in time. It ties that document to whoever controlled the sealing channel: attribution by control, and every proof page states exactly that.