Prove a file existed, exactly as it is now
Drop any file. Your browser computes its SHA-256 fingerprint and sends only that. You get two independent RFC 3161 timestamps, a Bitcoin anchor, and a permanent link anyone can check.
A seal establishes three things: the file existed at a point in time, it has not changed since, and you held it.
What a seal gives you
- Hashing runs in your browser with the Web Crypto API, so the file stays on your device.
- Two independent RFC 3161 timestamp authorities sign the fingerprint, not one.
- A Bitcoin anchor through OpenTimestamps, plus records in Sigstore Rekor, GitHub, and GitLab.
- A Personal Document Seal you can check offline in any authenticator app.
- A permanent verify link, and the raw timestamp files to download.
- No account needed to seal your first file.
Questions
Is this copyright registration?
No. In the United States, copyright is registered with the US Copyright Office and nothing else substitutes for it. A seal is evidence that a specific file existed at a specific time, has not changed since, and was in your hands.
Is this notarization?
No. A notarial act involves a commissioned notary confirming who you are. Abundera Sign offers remote online notarization as a separate product. A seal is a cryptographic timestamp.
Do you store my file?
Never. Your browser computes the SHA-256 fingerprint and only that 64-character string is sent. The file cannot be reconstructed from it.
How long does the Bitcoin anchor take?
Usually one to two hours, because OpenTimestamps batches submissions into a Bitcoin transaction. The two RFC 3161 timestamps are issued immediately, so the seal is complete the moment it is created.
What does a seal actually prove?
Three things: the file existed when the timestamps were issued, it is byte-for-byte identical to what was sealed, and whoever created the seal held the file. It is tamper-evident, so any change to the file breaks the match.
What file types can I seal?
Any of them. A seal works on the bytes, so a video, a design file, a contract, or a source archive all behave the same way.
Can someone seal a fingerprint they didn't create?
They can submit any fingerprint, but a seal only ever proves that fingerprint was known at that moment. To use a seal as evidence you must produce the matching file, and verification always shows the earliest seal for a fingerprint. Sealing a fingerprint you found somewhere leaves you with a later record and no file to back it.