A trusted timestamp certificate for any file, anchored via the OpenTimestamps calendars. Only a blinded 32-byte digest is sent — the file never leaves your browser.
A trusted timestamp certificate for any file, anchored via the OpenTimestamps calendars. Only a blinded 32-byte digest is sent — the file never leaves your browser.
Prove that a file existed at a certain moment without revealing the file. GhostProof computes the file's SHA-256 hash in your browser, blinds it with a random nonce, and submits only that blinded 32-byte digest — never the file, and never even the file's true hash — to the OpenTimestamps calendars, an independent network that anchors submitted digests into the Bitcoin blockchain. You get a certificate-of-timestamp PDF that embeds the hash, the nonce, and the calendar commitments, and anyone can later re-check that a file matches the certificate at /verify by confirming its SHA-256 equals the certified hash. Because the digest is blinded for your privacy, the embedded proof is verifiable through GhostX rather than by a stock OpenTimestamps client — we do not emit a portable .ots file. This is the one GhostX tool that contacts a third party, because a trusted timestamp inherently requires one — but even then, only a blinded 32-byte digest leaves your device. Useful for establishing prior authorship of a design, a contract draft, source code, or research. Free, no signup.
Drop your file
Drag any file onto the page or click to browse. It opens in the studio with Timestamp pre-selected — it works for any file type, not just PDFs.
Create the proof
GhostProof hashes the file locally and sends only that hash to the OpenTimestamps calendars for a Bitcoin-anchored timestamp.
Download the certificate
A certificate-of-timestamp PDF downloads from your browser, embedding the hash and the proof. Keep it — re-check it any time at /verify.
Is my file uploaded to timestamp it?
No. Only the file's SHA-256 hash — a 32-byte fingerprint that reveals nothing about the contents — is sent to the timestamp calendars. The file itself never leaves your browser.
How does the proof establish the time?
The hash is submitted to OpenTimestamps calendar servers, an independent network that aggregates submissions and anchors them into the Bitcoin blockchain on its own schedule. The certificate you download records the hash, the submission, and the calendars it was sent to; the portable, self-contained guarantee is that a file's SHA-256 matches the certified hash.
How do I verify a timestamp proof later?
Go to /verify and drop the certificate to read the certified hash, then confirm the file's SHA-256 equals it — that proves the file matches the certificate, and only the hash is ever needed. The independent Bitcoin anchoring is maintained by the OpenTimestamps calendars the hash was sent to.
Why does this tool contact a server when other GhostX tools don't?
A trusted timestamp inherently needs an independent third party — otherwise you could just claim any time. GhostProof keeps the privacy bar as high as possible: it sends only the hash, never the file, and every calendar it contacts is listed openly.
Can I verify this certificate with standard OpenTimestamps tools?
Not directly. To keep your file private, GhostProof blinds the hash with a random nonce before submitting it, so a stock OpenTimestamps verifier — which walks the proof from the file's own SHA-256 — can't reproduce the leaf. The nonce is stored inside the certificate, so the proof is fully reconstructable, but through GhostX rather than the public OTS ecosystem. We don't currently emit a portable .ots file. The guarantee that works entirely offline, with no third party at all, is the SHA-256 match at /verify.
What if the timestamp calendars are unreachable?
You'll still get a certificate, but it will be marked “Timestamp created (offline)” — meaning it records the hash and your device's clock with no Bitcoin anchor behind it. An offline certificate proves the file matches the hash; it does not independently prove when it existed. Re-run the timestamp when you're back online if you need the anchored proof.
Every GhostPDF tool runs entirely in your browser. Your file is never uploaded — there's no upload endpoint to send it to.