Most confidential, valuable resources on the World Wide Web are protected by some form of authentication technology. To access these resources, either via the public Internet or private intranets, users must verify their digital identity. This can range from a simple user-name-password combination to biometric data such as fingerprints to physical objects like hardware tokens and smart cards. Federated identity management would enable individuals to interact with various service providers or Web sites with trust relationships by signing in just once.