XML Signatures are digital signatures (digital signature: An electronic, encryption-based, secure stamp of authentication on a macro or document. This signature confirms that the macro or document originated from the signer and has not been altered.) designed for use in XML-based transactions. They are defined through a joint effort of the World Wide Web Consortium (W3C) (World Wide Web Consortium (W3C): A consortium of commercial and educational institutions that oversees research and promotes standards in all areas related to the World Wide Web.) and the Internet Engineering Task Force (IETF). XML Signatures contain a series of XML elements (XML element: An XML structure that consists of a start tag, an end tag, and the information between the tags. Elements can have attributes and can contain other elements.) and attributes (XML attribute: A name-value pair, separated by an equal sign and included in a tagged element, that modifies features of an element. All XML attribute values are strings enclosed in quotation marks.) that define various components needed to securely sign an XML document, including information about the location of the XML document to be signed, the algorithm used for signing, and information about the key used for signing.
An important feature of XML Signatures is the ability to have multiple digital signatures contained within one XML document. This allows multiple users to work on the same XML document, with each user providing a new digital signature on top of signatures added by other users.
Adding a digital signature to an XML document helps ensure that the data contained in the document is more secure, and that the identity of the person who signed the XML document can be verified.