Answer from ChatGPT

OpenID and OAuth are related but distinct protocols that serve different purposes in the context of web authentication and authorization.

OAuth (Open Authorization): OAuth is an open standard for access delegation. It allows a user (resource owner) to grant a third-party application (client) limited access to their resources on a resource server (typically owned by a different party) without sharing their credentials (e.g., username and password) with the client. OAuth is commonly used for enabling Single Sign-On (SSO) across different applications and services.

OAuth provides a framework for granting access tokens that represent specific scopes or permissions to access certain resources. These tokens are then used by the client to access the protected resources on behalf of the user. The OAuth protocol includes various flows, such as Authorization Code Flow, Implicit Flow, and Client Credentials Flow, to accommodate different use cases.

OpenID Connect (OIDC): OpenID Connect is an extension of OAuth 2.0 and serves as an identity layer on top of OAuth. It adds the ability to authenticate users, not just authorize access to resources. In other words, while OAuth deals with resource access, OpenID Connect deals with user authentication and providing identity information.

OpenID Connect introduces additional endpoints and claims to identify and authenticate users. It allows clients to obtain identity information about the user, such as their name, email, and unique identifier (sub), in the form of ID tokens. ID tokens are JSON Web Tokens (JWTs) that contain information about the authenticated user.

In summary:

• OAuth is primarily focused on access delegation and authorization, allowing third-party applications to access limited resources on behalf of the user without knowing the user's credentials.
• OpenID Connect builds on top of OAuth and adds authentication capabilities, enabling clients to verify the identity of the end-user and obtain user information.

Together, OAuth and OpenID Connect form a powerful combination for secure and user-friendly authentication and authorization in modern web applications, providing mechanisms for both granting access to resources and verifying the identity of users.

Answer from Bard

OpenID Connect is an extension of OAuth 2.0. It adds a number of features to OAuth 2.0, such as:

• User authentication: OIDC provides a way for the client to authenticate the user directly with the authorization server. This is done by using the Authorization Code Grant flow.
• ID tokens: OIDC defines a new type of token called an ID token. The ID token contains the user's identity information, such as their name, email address, and picture. This information can be used to personalize the client's experience.
• Userinfo endpoint: OIDC defines a new endpoint called the Userinfo endpoint. This endpoint can be used by the client to retrieve the user's profile information.

In addition to these features, OIDC also provides a number of other benefits, such as:

• Standardized: OIDC is a standardized protocol, which means that it is supported by a wide range of identity providers and clients.
• Secure: OIDC uses a number of security features to protect the user's identity and data.
• Extensible: OIDC is extensible, which means that it can be customized to meet the specific needs of different applications.

Overall, OIDC is a more secure and feature-rich protocol than OAuth 2.0. However, it is also more complex. If you need a simple and flexible authorization framework, OAuth 2.0 is a good choice. If you need a more secure and feature-rich authorization framework, OIDC is a good choice.