Which is the most commonly used standard for information exchange within a federated identity system? Response:

OAuth is primarily an authorization framework for granting limited access to resources, often used in conjunction with OpenID Connect for identity, but not a primary identity federation standard itself.

OpenID is an authentication protocol, with OpenID Connect providing identity built on OAuth 2.0, but it is not as universally adopted for broad enterprise federation as SAML.

SAML (Security Assertion Markup Language) has been the dominant standard for enterprise federated identity management for many years, enabling single sign-on (SSO) across disparate security domains. It is extensively used to exchange authentication and authorization data between an identity provider (IdP) and a service provider (SP).

WS-Federation is an older standard mainly for SOAP-based web services, and while it supports federation, its adoption is less widespread compared to SAML in general enterprise use cases.