When a CardSpace-enabled application or website wishes to obtain personal information about the user, the CardSpace software takes over the display of the computer and represents the stored identities as virtual information cards. The user selects the card to use and the CardSpace software contacts the issuer of the identity to obtain a digitally signed XML document that contains the requested information.

CardSpace allows the users to create self-signed identities for themselves, which can, for example, replace the need to remember usernames and passwords to log in to websites. Other transactions may require a certified identity issued by a trusted identity provider, such as a bank or a governmental agency.

Windows CardSpace is built on top of Web Services Protocol Stack, an arguably open set of XML-based technologies, including WS-Security, WS-Trust, WS-MetadataExchange and WS-SecurityPolicy. CardSpace competes with other Internet identity architectures like YADIS and Liberty Alliance, though in some ways the three standards can be seen as complementary.

In February 2006, IBM and Novell announced that they will back the Higgins trust framework to provide a development framework that subsumes a support for the Web Services Protocol Stack underlying CardSpace within a broader, extensible support for diverse other identity-related technologies, such as SAML and Yadis. In this light, initial reports in the mainstream media positioning Higgins as a direct competitor for InfoCard  look to have been somewhat misconstrued.

Microsoft plans to include Windows CardSpace in upcoming products like Windows Vista and Internet Explorer 7. It is also included as part of Microsoft’s upcoming .NET Framework 3.0, which will support Windows XP and Windows Server 2003.

Offical Site – Windows Cardspace

On Wikipedia