Have you ever clicked "Sign in with Google" instead of creating a new account for a website?
If so, you've already used Identity Federation.
Identity Federation allows applications to trust a central identity source, known as an Identity Provider (IdP), to authenticate users. Instead of managing separate usernames and passwords for every application, users can sign in once and access multiple services.
Identity Federation in Action
Imagine your company uses:
- Slack
- Jira
- Salesforce
Without identity federation, you would need separate credentials for each application.
With identity federation, you sign in using your company account, and the other applications trust that authentication. This creates a smoother and more secure user experience.
This capability is known as Single Sign-On (SSO).
Key Components
Identity Provider (IdP)
The system that verifies a user's identity. Examples include Microsoft Entra ID, Okta, Google Identity, and Keycloak.
Service Provider (SP)
The application a user wants to access, such as Slack, Jira, or Salesforce.
When an application claims to support federation, it means it can integrate with external Identity Providers and trust them for user authentication.
Common Federation Protocols
OAuth 2.0
OAuth 2.0 is an authorization framework that allows applications to access resources on a user's behalf without requiring their password.
For example, a photo-printing app can request access to your Google Photos account. After you approve the request, Google grants the application limited access without exposing your password.
OpenID Connect (OIDC)
OpenID Connect (OIDC) is built on top of OAuth 2.0 and adds user authentication.
When you click "Sign in with Google", OIDC helps the application verify who you are and obtain basic profile information, such as your name or email address.
SAML
Security Assertion Markup Language (SAML) is an XML-based standard used to exchange authentication information between an Identity Provider and a Service Provider.
SAML is commonly used in enterprise environments to enable Single Sign-On across multiple business applications.
Identity Federation enables organizations to centralize authentication and provide Single Sign-On across multiple applications.
The most common technologies involved are:
- OAuth 2.0 for authorization
- OIDC for authentication and identity information
- SAML for enterprise Single Sign-On
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