Which term describes a central authentication protocol that allows users to log on once and access all systems they are authorized to use?

• A. Access Management
• B. Federation
• C. Identity Store
• D. Single Sign-On

Answer: (D)

Single Sign-On lets a user authenticate once with a central authority and then access multiple systems without re-entering credentials. The central identity provider verifies the user, issues a trusted token or session, and each connected application accepts that token to grant access. This streamlines the login experience while maintaining security through centralized control, revocation, and standard protocols like SAML, OAuth, or OpenID Connect that enable trusted token-based access across services.

Access management is about enforcing who can access what through policies and roles, but it isn’t the one-login mechanism itself. Federation describes trust and identity sharing across organizations or domains, enabling SSO across boundaries, but the description here focuses on the single-login mechanism rather than the cross-domain trust relationship. An identity store is simply where identities and credentials are stored; it supports authentication but is not the protocol that enables logging in once for multiple systems.