Document integrity & audit

A signed document is only worth as much as the proof that it wasn't altered after the fact. HridaSign keeps two records for that: a cryptographic fingerprint and an append-only audit trail.

The document fingerprint

When every signer finishes, the backend computes a SHA-256 hash over a deterministic fingerprint of the document:

• the title and the source file id
• every signed field's value, in a fixed order (sorted by field id)
• each recipient's signing metadata

The hash is stored on the SignDocument (document_hash).

Verifying it

GET /api/sign/{docId}/integrity recomputes the fingerprint from the current state and compares it to the stored hash:

{
  "documentId": 42,
  "intact": true,
  "storedHash": "…",
  "computedHash": "…",
  "message": "Document integrity verified"
}

If a stored field value or recipient record has been changed, intact is false and the message reads TAMPERED — hash mismatch. The check itself is logged as INTEGRITY_CHECK_PASSED or INTEGRITY_CHECK_FAILED.

The audit trail

GET /api/sign/{docId}/audit returns every event on the document, append-only, each row capturing the actor's email, IP address, user-agent, a timestamp, and optional metadata:

Action	When
DOCUMENT_CREATED · DOCUMENT_SENT	The owner sets it up and sends
DOCUMENT_VIEWED	A recipient opens their link
OTP_SENT · OTP_VERIFIED · OTP_FAILED	Email-OTP identity checks
DOCUMENT_SIGNED · DOCUMENT_DECLINED	A recipient signs or refuses
DOCUMENT_COMPLETED · DOCUMENT_CANCELLED · DOCUMENT_EXPIRED	Terminal states
INTEGRITY_CHECK_PASSED · INTEGRITY_CHECK_FAILED	A verification was run

Together the fingerprint answers "is this the document that was signed?" and the trail answers "who did what to it, from where, and when?".