What is Identity Federation Protocols?

Understanding Identity Federation Protocols

Identity federation protocols are the standards that enable secure authentication and authorization to be shared across different systems and organizations. They let an identity provider (IdP) vouch for a user's identity to relying service providers (SPs), so users access resources in multiple trust domains without maintaining separate credentials in each one.

The core protocols serve distinct purposes. SAML 2.0 is an XML-based standard that exchanges signed authentication assertions between an IdP and SP, widely used for enterprise web single sign-on. OAuth 2.0 is an authorization framework that issues access tokens granting delegated access to APIs without sharing passwords. OpenID Connect (OIDC) builds an authentication layer on top of OAuth 2.0, adding an ID token (a JWT) that proves who the user is. Trust is established through pre-shared metadata and cryptographic signatures on tokens and assertions.

These protocols matter because they centralize authentication, which both strengthens security and improves usability. A single IdP can enforce strong MFA, conditional access, and instant deprovisioning, so disabling one account cuts off access everywhere. They reduce password sprawl and reuse, a leading cause of breaches. However, they also concentrate risk: a compromised IdP or a stolen, unexpired token can grant broad access, so token validation, short lifetimes, and signature checking are critical.

For example, an employee signs in to their corporate Microsoft Entra ID account, then clicks to open Salesforce. Salesforce, acting as the SP, redirects the browser to the IdP, which has an active session and returns a signed SAML assertion. Salesforce validates the signature and logs the user in automatically, granting access without a second password prompt while honoring the MFA already satisfied at the IdP.