In a federated system, which system validates the identity of a user and is used by the service provider to obtain the identity of the current user?

• A. Identity Provider (IdP)
• B. Identity Store
• C. Directory Service
• D. Credential

Answer: (C)

In federation, the thing that validates the user’s identity and provides proof to the service provider is the Identity Provider. The IdP authenticates the user (often by prompting for credentials) and then issues a signed token or assertion that the service provider can trust to know who the current user is. The service provider relies on that assertion to authorize access and identify the user across domains. An Identity Store or Directory Service simply holds user records and does not itself perform cross-domain authentication or issue federated proofs, while a Credential is just the secret used to prove identity, not the system that issues identity assertions.