What Is Authentication vs. Authorization?

Authentication and authorization are two distinct but complementary security functions. Authentication verifies who you are, confirming your identity. Authorization determines what you can do, granting or denying access to specific resources or actions based on your verified identity. Understanding the distinction helps organizations build secure systems that properly control both identity verification and access management.

Authentication: proving identity

Authentication answers the question "Who are you?" It's the process of verifying that someone is who they claim to be, typically by requiring them to prove something they know (a password), something they have (a phone or security key), or something they are (a fingerprint or face).

Standard authentication methods include username and password combinations, the traditional approach where users prove identity by providing a secret only they should know. Multi-factor authentication adds an extra layer of verification, requiring users to prove their identity through multiple independent factors. Biometric authentication utilizes physical characteristics, such as fingerprints, facial features, or iris patterns. Cryptographic authentication uses digital signatures or challenge-response protocols with private keys.

Strong authentication is fundamental to security. If a system cannot reliably verify who is accessing it, all other security controls become meaningless. An attacker who successfully impersonates a legitimate user gains the same access that the user has.

Authorization: granting access

Authorization answers the question "What can you do?" After authentication confirms identity, authorization determines what resources and actions that identity is permitted to access.

Authorization decisions are typically based on roles assigned to users (role-based access control), specific permissions granted to individual users, attributes about the user such as department, clearance level, or job function, or policies that evaluate contextual factors like time, location, or device.

Authorization is separate from authentication. Knowing who you are doesn't automatically determine what you can access. Two authenticated users might have very different permissions, an administrator can modify system settings, while a regular user can only read data.

How they work together

In practice, authentication and authorization operate in sequence. The user proves their identity through authentication. The system looks up the permissions that the identity has. The system grants or denies access based on those permissions.

A practical example: An employee logs into a corporate system using their username, password, and a code sent to their phone (two-factor authentication). The system confirms their identity and checks their role. As a member of the finance team, they can access financial reports but not engineering documents (authorization).

Protocols and standards

Different protocols handle authentication and authorization. Single Sign-On (SSO) enables centralized authentication, allowing users to log in once and access multiple applications without re-authenticating. Benefits include easier user experience, lower risk of password reuse, and simplified management.

WebAuthn enables passwordless authentication using public key cryptography. Developed by the W3C and FIDO Alliance, it enables users to authenticate with biometrics or security keys instead of passwords, offering stronger security with improved usability.

OAuth 2.0 handles authorization, allowing users to grant applications limited access to their resources without sharing credentials. When you authorize an app to access your photos or calendar, OAuth manages that permission grant.

OpenID Connect adds an identity layer on top of OAuth 2.0, enabling applications to authenticate users while also using OAuth 2.0 for authorization to protected resources.

Authentication and authorization in digital identity

Digital identity systems involve both concepts. When you present a mobile driver's license, authentication occurs at multiple levels: the wallet authenticates you through biometrics or a PIN before granting access to the credential, and the credential itself verifies its origin through cryptographic signatures from the issuing DMV.

Authorization appears in what the credential presentation permits. Proving you're over 21 authorizes age-restricted purchases. Proving you hold a valid license authorizes driving. Proving your identity to a bank authorizes access to your account.

Verifiers perform authorization decisions based on authenticated credentials. The credential provides cryptographic proof of its validity and issuer, while the wallet ensures that the presenter is authorized to use the credential. The verifier then makes authorization decisions based on the authenticated presentation.

Why the distinction matters

Confusing authentication and authorization creates security vulnerabilities. A system that properly authenticates users but poorly manages authorization might allow authenticated users to access resources they shouldn't. A system with strong authorization but weak authentication may have effective access controls that are easily bypassed through impersonation.

Secure systems require both reliable authentication to confirm identity and properly designed authorization to control what authenticated identities can access. The protocols and standards that support digital identity, including SSO and WebAuthn, as well as OAuth and OpenID Connect, work together to provide both functions in a secure and interoperable manner.