Introduction to Identity Federation
What is Identity Federation?
A federated identity in information technology is the means of linking a person's electronic identity and attributes, stored across multiple distinct identity management systems.
It is related to single sign-on (SSO), in which a user's single authentication ticket, or token, is trusted across multiple IT systems or even organizations. SSO is a subset of federated identity management, as it relates only to authentication and is understood on the level of technical interoperability and it would not be possible without some sort of federation.
With the identity federeation we get to separate the applications and, the login and get permissions process. Currently, there are two mainstream identity federation standards: SAML and OpenID-Connect.
SAML (Security Assertion Markup Language)
SAML is an important component of many SSO systems that allow users to access multiple applications, services or websites from a single login process. SAML allows sharing security credential across systems.
OpenID-Connect
OpenID-Connect is based on most modern protols. It uses JSON tokens, signed and optionally encripted using JWT standard, and uses simple REST as its transport protocol.
Sometimes referred as OpenID, must not be confused with an older and deprecated standard named OpenID.