Authentication vs Authorization: The Twin Pillars of IAM

🔑 What Is Authentication? — “Who Are You?”

Authentication is the process of verifying a user’s identity. Its purpose is to ensure the person attempting to access a system is legitimate.

Common Authentication Methods

• Passwords or PINs

• Multi-Factor Authentication (MFA)

• Biometrics (face scan, fingerprint)

• Digital certificates

• Token-based authentication

Example

When a user signs in to Azure AD using their username, password, and an MFA OTP, Azure AD is performing authentication.

🛡️ What Is Authorization? — “What Can You Do?”

Authorization decides what actions a verified user is allowed to perform inside a system. It is typically based on roles, permissions, and policies.

How Authorization Works

• Role-Based Access Control (RBAC)

• Policy enforcement (e.g., JSON IAM policies)

• Attribute-based access control

• Resource-level and action-level permissions

Example

An authenticated AWS IAM user may be authorized to:

• ✅ Read objects from an S3 bucket

• ❌ But not delete them

This is authorization controlling the permitted actions.

⚙️ How Authentication & Authorization Work Together

Although separate, authentication and authorization always operate in sequence:

1. Authentication – Confirms the user’s identity

2. Authorization – Checks what the user is allowed to do

Together, they form the foundation of Zero Trust Security, where no user is assumed to be trustworthy by default.

💡 Real-World Scenario: OpenShift

In OpenShift, the flow works like this:

• Authentication:
  A developer logs in via OAuth (e.g., GitHub, LDAP, Google).

• Authorization:
  OpenShift RBAC then determines what they can do, such as:

  • Deploying pods

  • Accessing specific namespaces

  • Modifying cluster settings

Without both, the platform cannot reliably protect clusters, workloads, or user data.