The main document describing this format is the ETSI TS 101 733 Electronic Signature and Infrastructure (ESI) – CMS Advanced Electronic Signature (CAdES).
The CAdES format has 6 different profiles defined, depending on the level of protection offered. Each profile includes and upgrades the previous one. Currently, at Viafirma, we support up to the CAdES-T profile:
CAdES
Basic form that simply meets the Directive legal requirements for the advanced e-signature
CAdES-T (timestamp)
The time-stamped field is incorporated into it to protect the data from possible repudiation.
CAdES-C (complete)
It is a CAdES-T to which references about the certificates and revocation lists are added and used to allow offline validation and verification in the future (without storing the current verification data).
CAdES-X (extended)
It is a CAdES-C to which information about the date and time of the data entered for extension C is added.
CAdES-X-L (extended long-term)
It is a CAdES-X to which certificates (public key only) and validation sources are incorporated. Ensures long-term off-line validation even if the original source is not available.
CAdES-A (archived)
This format includes all the above but includes meta-information regarding re-signaturing policies. A re-signaturing policy establishes an expiry date of the digital signature and afterwards the re-signaturing process begins. The ideal scenario for this signature format are those documents with a very long validity period: mortgages, university titles, deeds, etc. 15, 20, 50 years, etc.