PAdES

Description

While PDF and ISO 32000-1 provide a framework for digitally signing their documents, PAdES specifies precise profiles making it compliant with ETSI standards for digital signatures (Advanced Electronic Signature - AES and Qualified Electronic Signature - QES). ETSI (European Technical Standards Institute) has the function of issuing technical standards by delegation in the EU eIDAS Regulation (European Union Regulation on electronic identification and trust services for electronic transactions in the internal market). The eIDAS regulation enhances and repeals the Electronic Signatures Directive 1999/93/EC. EIDAS is legally binding and in all EU member states since July 2014 and unlike the Directive it replaces, the eIDAS as a Regulation is directly applicable without implementing or interpreting legislation. Any electronic signature recognised under eIDAS (including ‘click accept’) cannot be denied validity and effectiveness by reason of being electronic. If it is a ‘digital signature’ that is, an electronic signature implementing digital certificates in compliance with the advanced or qualified described in eIDAS (and their implementations developed by ETSI from a technology level) it can support PAdES. AES and QES have a higher evidentiary value than simple or ‘standard’ electronic signatures. QES is recognised the same legal value as a handwritten signature.

PAdES standards travel in the same direction and have the same aims as digital signatures (AES and QES). This means they can be easily verified in any PDF reader and as

• it is uniquely linked to the signatory (in QES to the identity of the signatory);
• it is capable of identifying the signatory (‘attribution’);
• only the signatory has control of the data used for the signature creation (in QES control and custody, as a portable token or ID and authentication where a certificate is downloaded for each use from a cloud ID provider);
• it can be, in PAdES easily, identified if data attached to the signature has been changed after signing.

PAdES has 4 levels of verification for digital certificate, from the most simple and basic (b-b, indicating a signature was executed with a certificate that was valid on a date) to the most complex (b-LTV) allowing electronically signed documents to remain valid for long periods (long term validity) even if underlying cryptographic algorithms or the other certificates expired.

As PAdES recognizes that digitally-signed documents may be used or archived for many years, and may need to be evidenced in court, once signer certificates have expired (after a few months on b-b) they can be enquired by contacting the certification authority. In b-lt or b-LTV (the most complex) certificates remain valid for a very long term. PAdES allows certificates to be verified even after many decades at any time in the future, in spite of technological and other advances. If in the document itself the validar to confirm that the signature was valid is concept known as long-term validation (LTV).

The PAdES standard, ETSI European Standard (EN) 319 142, introduces a number of adaptations and extensions to PDF to satisfy the Directive's requirements. ETSI will feed these European-specific elements back into ISO for inclusion in the next release of the PDF standard, ISO 32000-2.