How Blockchain Document Verification Works

Blockchain document verification is a way to prove that a document existed in an exact form at a certain time, using a public ledger that nobody can quietly edit. In PenMarker it is an optional extra on top of sealing: once everyone has signed, you can record the sealed document's fingerprint on the XRP Ledger.

This post explains what a fingerprint is, what PenMarker records and what it doesn't, and how you can use the record later.

What is a document fingerprint?

A fingerprint is a short value calculated from a file with a hash function. PenMarker uses SHA-256, which turns any file into 64 hexadecimal characters.

Two things make it useful:

• the same file always gives the same fingerprint;
• changing a single character in the file gives a completely different fingerprint.

So if two copies of a PDF have the same SHA-256 fingerprint, they are the same file, byte for byte.

What happens when a document is sealed?

When the last signer signs, PenMarker seals the document:

1. It produces the final PDF, with every signature in place.
2. It calculates the SHA-256 fingerprint of that sealed file.
3. It closes the audit trail. Every event (sent, viewed, signed, sealed) is recorded with its time and IP address, and each event's hash is chained to the one before it, so an edited or removed event breaks the chain.
4. It keeps the sealed copy in your archive, with a certificate of completion.

Sealing happens for every document. Recording it on a blockchain is your choice.

What PenMarker records on the XRP Ledger

When you choose Record on-chain, PenMarker records one hash per sealed document: the fingerprint of the document's manifest. The manifest is a short description of the sealed document: its name, its PenMarker id, the sealed file's fingerprint, the signers and the time it was sealed.

That one hash goes into a memo on an XRP Ledger transaction sent by PenMarker's own wallet. The document itself never leaves PenMarker, and no names or email addresses are written to the ledger, only the 64-character hash.

The XRP Ledger closes a new ledger every few seconds, so a record usually confirms within 5 to 10 seconds. PenMarker then shows the transaction, the ledger it's in, and a link to a public XRP Ledger explorer.

Why use a public ledger at all?

Sealing and the audit trail already show that a document hasn't changed since it was signed. A public ledger adds a record that is independent of PenMarker:

• it carries the ledger's own timestamp;
• it can't be edited or deleted afterwards, by anyone, including PenMarker;
• anyone can look the transaction up on a public explorer, without a PenMarker account.

How do you verify a document later?

In your PenMarker archive, choose Verify a file and drop in the PDF. PenMarker calculates its SHA-256 fingerprint and looks for a match in its own records of sealed documents. You then see one of two results:

• Verified: the file matches a sealed copy, with the date it was sealed and its folder;
• No match: the file wasn't sealed by PenMarker, or it has been changed since.

When the document was also recorded on-chain, its archive entry links to the XRP Ledger transaction, so you can show the independent timestamp too.

What a ledger record does and doesn't prove

A ledger record proves that a document with that fingerprint existed at that time. It doesn't prove what the document means, who should have signed it, or that it is enforceable. Those questions depend on the document, the signing process and the law that applies. See Security and compliance for how PenMarker supports electronic signatures under the ESIGN Act, UETA and eIDAS.

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