Definition
Federated identity, also known as identity federation, is a system that allows users to access multiple independent systems or applications using a single set of credentials. It works by establishing trust between different identity providers and service providers, so a user authenticates once with their home identity provider and is granted access to other trusted services. This simplifies user management, enhances security by reducing password fatigue and the need to store credentials in multiple places, and improves the user experience. For example, using your Google account to log into a third-party website is a form of federated identity. It is distinct from single sign-on, which typically operates within a single organization's network, whereas federation often spans multiple organizations. This concept is crucial for understanding modern access control and appears on exams like CompTIA Security+ and CISSP.