How authentication works

What happens when you authenticate a document, and what each step is there to prevent.

Authenticating a document takes about as long as attaching it to an email. Underneath, five things happen, and each one exists to close off a specific way documents get faked.

1. Your document gets a fingerprint

The moment you choose a file, your browser calculates a fingerprint of it. A fingerprint is a short string of characters derived from the contents of the file, using SHA-256, a standard published by the US National Institute of Standards and Technology.

Two properties are what make it useful:

The same file always produces the same fingerprint.
Any change at all produces a completely different one. Not a similar one. A totally unrelated one. Editing a single digit, deleting a space, or re-saving the file is enough.

The fingerprint is calculated on your device, and only the fingerprint is sent to Audrie. Your document stays with you.

A fingerprint cannot be reversed. Nobody holding it can work out what your document said, or reconstruct any part of it. It is only useful for comparing against another file you already have.

2. You prove it is you

Before anything is authenticated in your name, you confirm it with a passkey. A passkey lives on your device and is unlocked the way you already unlock it, with a fingerprint reader, face unlock, or your device PIN.

This replaces passwords deliberately. A password can be guessed, reused, phished, or leaked in somebody else's breach. A passkey cannot: there is nothing to type, nothing to copy, and nothing useful for an attacker to steal from a server. Approving an authentication requires your physical device, in your hand, at that moment.

Your approval is also short-lived and scoped to authenticating documents. It expires quickly, and it cannot be used for anything else.

3. Your identity is already verified

Passkeys prove that the same person came back. They do not, on their own, prove who that person is. So Audrie verifies your identity separately, and you cannot authenticate anything until that is complete.

Every certificate also records how your identity was established, either verified independently through Audrie's identity provider, or attested by your employer. Anyone checking a document can see which, so they are never guessing about the strength of the identity behind it.

4. Your document is signed

Audrie signs the record with ML-DSA-65, a signature standard published by NIST in 2024 as FIPS 204.

The reason for choosing it is worth understanding, because it is about the future rather than today. The signature schemes most of the internet runs on, RSA and elliptic-curve, are expected to be breakable by a sufficiently capable quantum computer. For a web session that hardly matters, because a session intercepted today is worthless by the time it could be broken. For a document it matters enormously. A deed, a trust instrument, or a company filing is supposed to still mean something in twenty or thirty years. A signature made with a scheme that gets broken in the meantime becomes worthless retroactively, taking the document's credibility with it.

ML-DSA-65 is designed to survive that. Signing a document today with it means the proof still holds later, which is the entire point of signing a document rather than a message.

If you are authenticating a PDF, you can also have a certificate page added to it. Your original content is preserved exactly, with the certificate added as a new page.

5. The record is committed to a public ledger

Finally, the record is committed to Hedera Consensus Service, a public ledger run by the Hedera Governing Council, a group of large international organisations. Audrie has no control over it and cannot alter what has been committed.

Hedera assigns the entry a timestamp and a permanent position in sequence. Neither can be changed afterwards, by us or by anybody else. This normally settles within a few seconds, and until it does, a verification honestly reports the record as still settling rather than claiming more than it can prove.

This is the step that means you do not have to take Audrie's word for it. The entry is public, and anyone can inspect it without our involvement. See verifying a document.

The committed entry is pseudonymous. It carries your document's fingerprint and the technical details a verifier needs to locate and check the record. It carries no document content, no filename, and no personal identity. The link between a ledger entry and a person exists only inside Audrie.

What you receive covers what you end up holding, and why there are two different kinds of proof.
What Audrie never sees covers exactly what is and is not stored.