Evidence and certificates

Somebody disputing a signature three years from now does not get a database. They get a PDF and a claim.

When a document completes, a certificate is issued: the document and its hash, every signer with the method and value of their signature, and the whole event chain with the address and browser at each step. It is frozen at issue and hashed.

Frozen, and checked against the live record

Freezing sounds like the wrong instinct — a derived value that has drifted is the one somebody quotes. But a certificate is evidence, and evidence says what was true at a moment. Deriving it later means the document somebody holds and the document we render can differ with nothing to compare.

So both properties are kept. The payload is frozen and hashed at issue, and verification re-derives it from the live record and reports any divergence:

{
  "certificate_found": true,
  "document_matches": true,
  "still_matches_record": false,
  "divergence": "The document text has changed since this certificate was issued."
}

The sealed PDF

GET /v1/documents/{id}/pdf returns the certificate as a PDF sealed with a PAdES detached signature and an RFC 3161 timestamp — over the signature, not over the document, which is what lets a reader tell when the seal was applied rather than when the file was made.

Public verification

Every certificate carries a sixteen-character code, printable and typable: no I, L, O or U, because those are the four that get mistyped as 1, 1, 0 and V. Anybody holding it can check the certificate without an account.