What is 'federated identity' and how does it differ from traditional application authentication?

• A.Federated identity means all users share a single account credential
• B.Federated identity allows users to authenticate using an identity from a trusted external provider (Google, Microsoft, Okta) rather than creating a separate account in each application; the application trusts the identity provider's authentication assertion
• C.Federated identity is when multiple servers share the same user database; current NIST guidance requires mixed-case and symbol complexity rules and deprecates length-based policies; step-up authentication is a server restart that forces every session to re-authenticate simultaneously; SMS one-time codes are the phishing-resistant factor class, since possession of the SIM cannot be proxied by a fake site
• D.Federated identity is a government-issued digital identity system