ISO 14533-3:2017

Overview

ISO 14533-3:2017 defines long-term signature profiles for PDF Advanced Electronic Signatures (PAdES). Its purpose is to ensure that electronic signatures embedded in PDF documents remain verifiable over long periods by specifying which PAdES elements (not new cryptographic algorithms) are required, optional, conditional or prohibited for long-term validation. The standard focuses on timestamping and preservation of validation data to detect illegal alterations and to maintain interoperability across implementations.

Key topics and technical requirements

• PAdES profiles for long-term validation
  • PAdES-T - protects the signature value using trusted evidence (timestamps). Three forms are defined: by document timestamp, by signature timestamp attribute, and by subsequent signature with a signature timestamp attribute.
  • PAdES-A - protects long-term availability and integrity of validation data that supports PAdES-T (e.g., certificate chains, revocation data).
• Required-level model (M / O / C / P)
  Elements in PAdES structures are labeled Mandatory (M), Optional (O), Conditional (C) or Prohibited (P). Implementations must include all Mandatory elements, may implement Optional elements, and must provide detailed specifications for Conditional elements.
• Signature Dictionary and validation metadata
  • The standard specifies required levels for entries in the PDF Signature Dictionary (CAdES-based PAdES usage), and how validation data and timestamps are represented and updated.
• Conformance and declarations
  • Generation and validation of PAdES-T and PAdES-A data must meet the document’s requirements. For first‑party conformity, implementers should provide a supplier’s declaration of conformity (Annex A) describing implementation status and handling of Conditional elements.
• Annexes and implementation guidance
  • Included normative and informative annexes cover timestamp-only profiles (Annex B), timestamp token structure (Annex C), using CMS signatures (Annex D), and multiple-signature examples (Annex E).

Practical applications

• Long-term archiving of signed PDF contracts, invoices, legal filings and regulatory records.
• PDF signing and validation software (desktop, server, cloud) that must ensure signatures remain verifiable years later.
• Digital archiving systems and records management that need to preserve signature integrity and validation evidence.
• Timestamp Authorities (TSAs), PKI operators and compliance teams implementing policies for signature lifecycle and proof-of-existence.

Who should use this standard

• PDF signing tool vendors and PDF viewer developers
• PKI and timestamp service providers
• Records managers, archivists and legal/compliance professionals
• Software architects designing long-term signature verification workflows

Related standards

• ISO 14533-1 (CAdES long-term signature profiles)
• ISO 32000-2 (PDF 2.0 specification)
• ETSI PAdES technical specifications (normative background)

Keywords: ISO 14533-3:2017, PAdES, long-term signature profiles, PDF advanced electronic signatures, PAdES-T, PAdES-A, timestamp, long-term validation, digital signature, interoperability.