In an online world it is tough to ensure the security and integrity of electronic signatures. For different scenarios something stronger than username and password is required, since the agreements and transaction consents may high value and high risk to both institution and customer.
The W3C and IETF's XML Signature specification allows the verification of the authenticity of XML-based transactions, a vital part of the emerging electronic business infrastructure. Ed Simon, Paul Madsen, and Carlisle Adams in O'Reilly XML.com, Aug. 08, 2001.
IETF/W3C XML-DSig WG's mission is to develop an XML compliant syntax used for representing the signature of Web resources and portions of protocol messages (anything referencable by a URI) and procedures for computing and verifying such signatures.