How a SeyAero custody anchor proves a record has not changed

1 · What the statement contains

A notarisation is a single canonical statement covering: the case reference; the audit chain head and length, recomputed from the stored rows; and the SHA-256 fingerprint of every exhibit byte held in storage, matched against the fingerprint recorded at ingest. The statement contains integrity facts only. It contains no evidence content, no personal data and no file bytes.

2 · Who signs it — two independent signatures

First, SeyAero. The canonical statement is hashed with SHA-256 and signed server-side with a ledger key that never leaves the platform. This proves the statement was issued by SeyAero and has not been altered since issue. It does not, on its own, prove when it was issued to someone who does not trust our own records.

Second, an independent timestamp authority. The anchor hash is submitted to DigiCert's public RFC 3161 Time Stamping Authority, which countersigns it and returns a standard timestamp token embedding the certified time and an authority serial number. DigiCert has no relationship with the case, the investigator or SeyAero's records. Its signature is over the hash and the time — nothing else is disclosed to it.

Anchors issued before independent countersignature was introduced, or during an authority outage, are labelled plainly on the verification result. A failed timestamp never blocks issuance and is never silently omitted.

3 · How a court or expert verifies it

There are two levels of verification, and the second requires no trust in SeyAero.

Level one — online, no account. Enter the anchor identifier printed on the notarisation certificate at seyaero.com/verify. The statement is re-canonicalised, re-hashed and its signature re-checked against the ledger key. The result reports signature validity, audit-chain integrity, exhibit fingerprint coverage and the independent timestamp status.

Level two — offline, against the authority. The verification result exposes the raw RFC 3161 token. Base64-decode it to token.tsr and verify it with OpenSSL against the authority's own public certificate chain:

openssl ts -verify -digest <anchor hash> \
  -in token.tsr -token_in -CAfile <authority roots>

openssl ts -reply -in token.tsr -token_in -text   # inspect certified time and serial

A passing check establishes, through DigiCert's certificate chain rather than through SeyAero, that the exact anchor hash existed at the certified time. Any alteration to the underlying statement — even a single bit — changes the hash and fails the check.

4 · What this proves — and what it does not

The anchor proves three things:

• the statement was issued by SeyAero (server signature);
• it has not been altered since issue (SHA-256 hash);
• it existed no later than the certified time (independent RFC 3161 countersignature).

It does not prove that the underlying evidence was authentic when first uploaded, that the investigation's conclusions are correct, or that any court will admit it. Weight and admissibility are matters for the court or inquiry. SeyAero's role is to make the custody record independently checkable; the evaluation of that record belongs to the tribunal.

5 · Verifying exhibit fingerprints yourself

Each exhibit's fingerprint is a plain SHA-256 of the file bytes. Any party in lawful possession of a file can reproduce it with standard tools and compare it against the fingerprint recorded in the notarisation certificate:

sha256sum exhibit.bin        # Linux / macOS
certutil -hashfile exhibit.bin SHA256   # Windows

A match confirms the file produced to the court is byte-identical to the file the platform held when the anchor was issued.