OAuth 2.0 and OpenID Connect
To implement the Digital Identity Management Single Sign-on (SSO) solution, the OAuth 2.0 authorization (authZ) framework and its authentication (authN) extension, OpenID Connect (OIDC) are the most important concepts.
OAuth 2.0 was established as a standard way of transferring resources across multiple systems on the internet. However, that standard did not take into account user authentication or user-identifying data. As a result, different organizations would implement their own proprietary means of brokering that information to external systems. To fix this, OIDC was established as an identity-centric extension to the OAuth 2.0 standard.
Some of the terms in OAuth 2.0 have slightly different name under OIDC. Moreover, certain types of data that are not standardized under OAuth.2.0 are standardized under OIDC.

