OpenID Connect (OIDC) is an authentication protocol based on the OAuth 2.0 protocol. OAuth 2.0 is a framework designed to support the development of authentication and authorization protocols. It provides a variety of standardized message flows based on JSON and HTTP, used by OIDC to provide Identity services. OIDC is an attempt to make authentication a more integral part of the OAuth 2.0 protocol. Thus, OIDC is an add-on to the OAuth 2.0 protocol, developed as the successor to SAML 2.0 and OpenID.
OIDC lets developers authenticate their users across websites and apps without having to own and manage password files. Authentication can be done in three different ways using OIDC (the Authorization Code Flow, the Implicit Flow or the Hybrid Flow). Signicat has implemented the first one of the three, the Authorization Code Flow. This flow will be the one described in the section below as well as in the flow diagrams.