Security and evidence
An electronic signature is only as strong as the evidence behind it. This is exactly what Pensti records, and how it can be checked.
1. Document fingerprint
Every PDF version gets a version number and a SHA-256 hash. When the document is sent, the version and hash are frozen (“SHA-256 before signing”). On every signature the hash is recomputed from the exact bytes, and signing is refused if a single byte has changed. The final sealed PDF gets its own hash.
2. Explicit intent
Pensti does not rely on a link having been visited. The process is recorded step by step: the link is opened (every time), the email address is verified through the unique link, the document is displayed, the recipient consents with the exact wording, fields are completed, the signature is adopted (drawn or typed), and the recipient actively clicks “Accept and sign”. Without that click, signing is not possible.
3. Append-only audit trail
Every event is stored with server time, actor, document, document hash and version, request and session id, IP address and device. Each event is hash-chained to the previous one, and the database rejects updates and deletions. Even with database access, history cannot be rewritten without verification failing.
4. Trusted timestamps (RFC 3161)
After each signature the audit trail's latest hash is timestamped by a timestamp authority, and the final PDF's hash is timestamped on completion. Timestamps can be downloaded and checked independently of Pensti, for example with OpenSSL.
5. Sealed PDF and certificate of signature
The final PDF contains the signatures, a certificate of signature with times, email verification, IP, location and device for each signer, and the full audit trail. Every page carries a document reference and page number. A machine-readable evidence file (JSON) is embedded, and the PDF is sealed with PAdES so PDF readers show if the file is changed afterwards.
6. Public verification
The QR code on the certificate leads to a verification page where anyone can check a file: the hash is computed in the browser and only the hash is sent to Pensti. Details are only shown when the file matches exactly.
Legal framework
Pensti provides simple electronic signatures (SES) under eIDAS Article 3(10), which cannot be denied legal effect solely because they are electronic (Article 25). Later changes to a signed document are detectable. Pensti does not currently provide advanced (AdES) or qualified (QES) signatures. If an agreement requires a specific form of signature, check with your legal adviser.