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Verify a document

Check whether a document was recorded by PDFengine and when an independent party first confirmed it existed.

How it works

  1. 1. Supply the document, the proof package (.zip) or the verification code.
  2. 2. We compute the fingerprint and look it up in the anchored trees.
  3. 3. You get three separate checks: the bytes, the tree and the independent confirmation.
or

This page is a convenience. The proof package that comes with a document verifies offline with standard tools, without PDFengine and without trusting us.

Without an independent check

  • The date in the file properties comes from a computer clock and takes a few clicks to change.
  • "Sent on" in a mailbox says when a message passed through, not what the attachment contained at the time.
  • A screenshot of a PDF viewer shows what you see, not that the file has been untouched since.
  • One green tick summarising everything does not help when the other side disputes exactly one part.

With this verification page

  • Three separate checks: the bytes, the place in the anchored tree and the confirmation by a third party.
  • Our own moment and the independent moment are shown apart, and named as such.
  • Public and account-free, so the recipient of a document can check it themselves.
  • And if you would rather not trust us at all: the proof package verifies offline with openssl.

How it works

1

Supply the file or the code

Dropping works too. The proof package carries the expected fingerprint, which is what lets us tell "changed" apart from "never seen".

2

We look up the fingerprint

Only the SHA-256 fingerprint goes into the lookup. Your file is not kept, and the result never names a filename, customer or content.

3

Read the three checks separately

Bytes, tree and timestamp are reported apart. Anyone contesting a proof wants to know which part holds, not one tick summarising everything.

Check it yourself, without PDFengine

This is the real check. It runs on your machine, needs only openssl, and does not involve us.

Request the proof package that belongs to the document. It is a ZIP holding these files:

  • proof.json — your document's fingerprint, the sibling hashes, the root and which timestamp authority signed.
  • README.txt — the same steps as below, included so the package still stands on its own ten years from now.
  • timestamp.tsr — the RFC 3161 timestamp token over the root.
  • tsa-chain.pem — the certificate chain of the timestamp authority.
  1. 1

    Compute your file's fingerprint

    The result must match the sha256 field in proof.json exactly. If it differs, the file was altered or re-saved.

    shasum -a 256 your-document.pdf

# Windows:
certutil -hashfile your-document.pdf SHA256
  2. 2

    Recompute the root

    Your document is one leaf in a tree per RFC 6962. Hash a leaf as SHA256(0x00 || digest bytes) and each internal node as SHA256(0x01 || left || right), placing each sibling from sibling_hashes on the side its position field states. A node without a sibling is promoted unchanged and never duplicated. What you end up with must equal root_hash in proof.json.

    leaf = SHA256(0x00 || sha256_of_your_document)
node = SHA256(0x01 || left || right)

# repeat with every sibling in sibling_hashes
# until you end up with root_hash from proof.json
  3. 3

    Fetch the root certificate yourself

    From the EU Trusted List or the authority's own publication — not from our package. Checking a token against a certificate that travelled with it proves only that the package is internally consistent. proof.json records the fingerprint of the root we used, so you can confirm you fetched the same one.

  4. 4

    Verify the timestamp token

    For an anchored round you verify the token over the root. If proof.json states an anchor_type other than merkle, skip step 2 and verify the token directly over the document.

    openssl ts -verify -digest <root_hash> -in timestamp.tsr \
    -untrusted tsa-chain.pem -CAfile <root you fetched yourself>

# separately stamped document (no tree):
openssl ts -verify -data your-document.pdf -in timestamp.tsr \
    -untrusted tsa-chain.pem -CAfile <root you fetched yourself>

Careful: re-saving changes the bytes. Even a document you merely open and save in Acrobat gets a different fingerprint, while nobody touched the content. Keep the original file exactly as you received it.

What this check proves: that the document existed no later than the moment shown, in exactly this form, and has not changed since. Not who created it, and not that its content is true.

When do you use this page?

Usually you are not the author of the document, but the recipient.

You received a document with a verification line

There is a code at the bottom of the document. Paste it here and you see when an independent party confirmed this document existed — without having to take the sender at their word.

You want to know whether anything changed

Bring the proof package along. Then we can tell "this file has been changed" apart from "we do not know this file". Without the package those two look identical.

You have to present the proof to a third party

A lawyer, auditor or judge does not want a web page but a check they can run themselves. Hand over the proof package and point at the steps above.

Frequently asked questions

What exactly does this check prove?

That the document existed no later than the moment shown, in exactly this form, and has not changed since. Not who created it, and not that its content is true.

Is my file stored when I upload it here?

No. A SHA-256 fingerprint is computed to run the lookup; the file itself is not kept. A lookup also never shows a filename, customer or content — only anchoring data.

Why do I see "no proof recorded" when the document is fine?

For a bare file we look up the fingerprint. One changed byte — including a re-save in Acrobat — produces a different fingerprint and therefore no record. If you have the proof package or the verification code, use those: with them "changed" can be told apart from "never seen".

Do I have to trust PDFengine to run this check?

No, and that is the point. The proof package verifies offline with openssl, against a root certificate you fetch yourself via the EU Trusted List. This page is a convenience, not a link in the proof.

What does "qualified" mean for the timestamp?

That the timestamp was issued by a qualified trust service provider on the EU Trusted List. Under Article 41 of eIDAS the date, time and integrity then enjoy the legal presumption of accuracy — the other side has to show it is wrong.

Why can the confirmed moment be later than the moment of recording?

Documents are anchored in rounds. We record your document immediately; the independent confirmation follows in the next round. The real moment of existence is therefore at or before the time shown, never after it.

Can I check an email or another file type as well?

Yes. The check runs on the bytes of the file, so the file type does not matter. An .eml or .msg works just as well as a PDF, as long as the file is exactly as it was recorded.

Three kinds of proof, three different questions

They look alike but do not answer the same thing. Here is which one you need when.

Fingerprint

Answers the question
Does this version differ from that one, and in what respect?
Where the proof lives
In a token and a JSON file you keep yourself.
When it is ready
Immediately.
Visible in Acrobat
No.
Works on
PDF, Office, images and email with attachments.
Cost
1 credit per file.

Proof package You are here

Answers the question
Did this file already exist at that moment, and is it unchanged since?
Where the proof lives
In a separate ZIP alongside your document, verifiable offline.
When it is ready
Anchored in the daily run; requesting one stamps immediately.
Visible in Acrobat
No.
Works on
Anything you convert here.
Cost
Included with the conversion; downloading needs a paid subscription.

Qualified timestamp

Answers the question
Did this document already exist at that moment — and can the recipient see it straight away?
Where the proof lives
Inside the PDF itself, as a PAdES DocTimeStamp.
When it is ready
Immediately.
Visible in Acrobat
Yes, green check mark.
Works on
Any PDF you upload, including files from elsewhere.
Cost
20 credits, paid account.

They do not exclude each other: one document can carry a fingerprint, a proof package and an embedded timestamp at the same time.

More evidence tools

Recording, comparing and stamping belong together.

Create a fingerprint

Compute the fingerprint of a file and record the form it existed in.

Compare two documents

See which layer two files differ on: bytes, text, appearance or metadata.

Qualified timestamp

Embed an eIDAS timestamp in your PDF, visible as a green tick in Adobe.

Check another document?

Free, no account, and your file stays yours.

Back to the check