XAdES (XML Advanced Electronic Signatures ) is a set of extensions to the W3C recommendation XML DSig, by the use of advanced electronic signatures is made possible.
While XML DSig is a general framework for the digital signature of XML documents, XAdES specifies precise profiles for XML DSig for use with authorized electronic signature in the meaning of the EU Directive 1999/93/EC. An important factor of XAdES is that electronically signed documents for a long time remain valid even if the underlying cryptographic algorithms have been cracked.
XAdES defines six profiles ( Forms), which differ in the offered protection factor. Each profile includes and extends the previous one:
- XAdES, basic shape satisfying than those in the directive provisions for the extended signature;
- XAdES -T ( timestamp ) timestamp has been added to provide protection from denial
- XAdES -C (complete), references to verification data (certificates and revocation lists ) were added to the signed documents to provide off-line verification and future verification ( the current data are not stored );
- XAdES -X ( extended), the references that were introduced with XAdES -C, timestamps are added to protect to protect against possible amendments of the certificates in the future;
- XAdES -XL ( extended long-term ), current certificates and revocation lists were added to the signed documents to allow future verification, even if the original source of verification data is not available;
- XAdES -A ( archival ), possibility of regular time stamp ( eg once a year ) of the archived document to prevent modifications that were caused by the signature to weaker during long-term storage.