Exploring OAuth, OpenID, and OpenID Connect: Key Differences and Use Cases

Introduction

Authentication and authorization are pivotal aspects of web and mobile application security. Through the years, three key protocols have emerged to facilitate secure and seamless user interactions: OAuth, OpenID, and OpenID Connect. Although they share common goals, each serves a distinct purpose and has unique functionalities. This article aims to clarify the differences between these protocols and illustrate their practical use cases.

OAuth - An Authorization Protocol

Purpose:
OAuth is primarily designed to handle authorization. It ensures that third-party applications can access a user's resources without obtaining their credentials.

How it Works:
OAuth operates through the exchange of tokens rather than user credentials. Here's a simplified process:

User Authorization: When a user grants access to a third-party application (like accessing their Spotify playlists), they are redirected to the service provider (e.g., Spotify). Login and Consent: The user logs in to their Spotify account and grants permission to the third-party application. Access Token Issuance: Upon user approval, the service provider issues an access token to the application. This token authorizes the application to access the user's data.

Example Use Case:
In a music app scenario, users allow the app to access their Spotify playlists by granting permission. They don't need to provide their Spotify username and password, ensuring enhanced security and user convenience.

OpenID - An Authentication Protocol

Purpose:
OpenID is an authentication protocol that simplifies user logins across multiple services using a single identity.

How it Works:
OpenID streamlines the login process by leveraging an OpenID provider (like Google or Yahoo). Here’s a breakdown:

User Registration: Users create an account with an OpenID provider. Single Sign-On: When logging into another service, users can use their OpenID credentials (e.g., Google login). Service Provider Authentication: The user is redirected to their OpenID provider for authentication. Once verified, they are redirected back to the service with a verified identity.

Example Use Case:
Imagine a scenario where a website integrates with Google for user authentication. Instead of creating a new username and password, users can log in using their existing Google account, streamlining the user experience.

OpenID Connect - Combining Authentication and Authorization with OAuth 2.0

Purpose:
OpenID Connect builds upon OAuth 2.0 to combine the strengths of both authentication and authorization. It authenticates users and authorizes access based on the identity provided.

How it Works:
OpenID Connect integrates seamlessly with standard OAuth 2.0 flows, adding an ID token that contains user information and is issued by the provider. Here's how it works:

OAuth Flow: Applications follow familiar OAuth 2.0 authorization flows. ID Token Issuance: Once the user is authenticated, an ID token is issued, containing data about the user and signed by the provider. This token can be used to verify the user's identity. Authoritative Verification: The ID token allows clients to confirm the user's identity, providing both authentication and authorization.

Example Use Case:
In a mobile app scenario, users can log in using their Google account. The app uses OAuth to access the app's resources while OpenID Connect verifies the user's identity, ensuring secure and verified access.

Summary

OAuth: Focuses on authorizing access to resources. OpenID: Specializes in authentication, confirming user identities. OpenID Connect: Combines both authorization and authentication, built on top of OAuth 2.0.

These protocols are often employed together in modern applications to offer secure and user-friendly authentication and authorization processes, enhancing both user experience and security.