XML Encryption, also known as XML-Enc, is a specification governed by a W3C recommendation, that defines how to encrypt the contents of an XML element.
The W3C XML Encryption standard specifies a process for encrypting data and representing the result in XML. The data may be arbitrary data (including an XML document), an XML element, or XML element content. The result of encrypting data is an XML Encryption EncryptedData element which contains (via one of its children's content) or identifies (via a URI reference) the cipher data.
When encrypting an XML element or element content the EncryptedData element replaces the element or content (respectively) in the encrypted version of the XML document.
When encrypting arbitrary data (including entire XML documents), the EncryptedData element may become the root of a new XML document or become a child element in an application-chosen XML document.
(source and further reading: http://www.w3.org/TR/xmlenc-core/)
