Introduction - Basic Concepts. Identity Lifecycle. Identity Assurance. Fundamental Technologies - Identity Provisioning. Single Sign On. Attribute Sharing. Privacy Enhancements. Standards and Systems - Overview. OASIS Security Assertion Markup Language (SAML). Liberty Alliance Identity Frameworks. OpenID. Information Card (CardSpace). Towards Harmonization. Research Prototypes. Emerging Areas. Challenges - Usability. Privacy Protection. Trust Management. Biometrics. Harmonization and Interoperability.