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Keyul Patel
Keyul Patel

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A Clear Guide to AuthN, AuthZ, OIDC, OAuth and Their Role in Securing Applications

If you’ve ever logged into an app using Google, granted an app access to your calendar, or seen terms like authentication and authorization, you’ve already interacted with concepts like AuthN, AuthZ, OIDC, and OAuth. These terms might sound technical, but their core ideas are easy to grasp.

This article will break down these essential concepts, explain how they work, and highlight their differences—all in simple terms. By the end, you’ll understand how modern apps secure your identity and control what you’re allowed to do.

AuthN, AuthZ, OAuth, OIDC

Credit: ChatGPT

What Is Authentication (AuthN)?

Authentication is all about proving who you are. Imagine trying to enter your school. At the gate, the guard asks, “Who are you?” You show your school ID, and they verify it’s you. That’s authentication in action.

Real-World Examples of Authentication:

  • Entering a username and password to log in. Using biometric authentication like fingerprints or facial recognition.
  • Receiving a one-time password (OTP) on your phone for login verification.

Purpose of Authentication:
The goal of authentication is to confirm your identity before allowing you to access a system. It answers the question, “Are you really who you claim to be?”


What Is Authorization (AuthZ)?

Once your identity is verified, the next question is: What are you allowed to do? This is where authorization comes in. Continuing the school analogy, imagine you’re now inside the school, but you want to enter the science lab. The lab has rules: only science students are allowed. The guard checks your timetable and confirms you’re a science student, then lets you in. That’s authorization.

Real-World Examples of Authorization:

  • A user can view files, but only an admin can edit or delete them.
  • A guest user can browse public pages, but a logged-in user can access their dashboard.
  • API endpoints that are restricted based on user roles (e.g., admin vs. user).

Purpose of Authorization:
Authorization controls what resources you can access and what actions you’re allowed to perform. It answers the question, “What are you permitted to do?”


What Is OAuth (Open Authorization)?

Think of OAuth as a secure way to allow someone to act on your behalf without sharing sensitive information. Here’s an example: You’re at a school fair, but you forgot your money. You call your mom and ask her to vouch for you. She calls the snack stand and arranges for you to get a ticket to buy snacks. The stand doesn’t need your mom’s credit card—they just trust the ticket.

This is OAuth: a protocol that lets apps or systems share limited access to your data without exposing your credentials.

Real-World Examples of OAuth:

  • Logging into an app using your Google, Facebook, or GitHub account.
  • Granting a fitness app access to your calendar to schedule workouts.
  • Allowing a social media app to access your photo gallery for uploads.

Purpose of OAuth:
OAuth enables delegated access to resources. It’s perfect for scenarios where one app needs access to your data from another app or service without compromising your security.


What Is OIDC (OpenID Connect)?

OIDC (OpenID Connect) builds on top of OAuth to add an authentication layer. In simpler terms, OIDC not only lets apps verify who you are (authentication) but also optionally grants access permissions (authorization).

Imagine you’re at a school fair in another state. The organizers don’t know you, but they trust your school ID. You show your school ID, and they recognize your identity and let you in. This is similar to how OIDC works.

Real-World Examples of OIDC:

  • Logging into a website with your Google account and verifying your identity.
  • Single Sign-On (SSO) systems that allow you to access multiple applications with one login.

Purpose of OIDC:
OIDC provides federated authentication, making it easy for apps to trust your identity across platforms. It’s commonly used for SSO solutions and scenarios where apps need both your identity and permission to access resources.


How Do OAuth and OIDC Differ?

Although OAuth and OIDC are often used together, they serve different purposes:

  • OIDC focuses on authentication, verifying your identity and optionally providing access.
  • OAuth focuses on authorization, granting apps limited access to your data.

For example, OAuth allows a travel app to access your calendar to book flights. OIDC takes it a step further by confirming that you are who you claim to be while granting the app permission.


Why These Concepts Matter for Developers

Understanding AuthN, AuthZ, OIDC, and OAuth is crucial for building secure, user-friendly applications. These protocols are the foundation of modern authentication and authorization systems, ensuring that users' identities and data remain protected while enabling seamless access to resources.

Whether you’re building a single sign-on system, integrating third-party APIs, or managing user roles, mastering these concepts will elevate your skills as a developer. Checkout quick summary here

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