How authentication and authorization differ
Authentication (often shortened to AuthN) is the act of proving an identity claim. It happens at the start of a session and relies on factors: something you know (a password), something you have (a phone or security key), or something you are (a fingerprint or face). The output of authentication is a verified identity, usually carried forward as a session or a signed token.
Authorization (AuthZ) comes after. Given a verified identity, the system decides whether this specific request is allowed: can this user open this record, approve this payment, delete this server? Authorization is evaluated continuously, on every request, against roles, group memberships, attributes, and policies. A user is authenticated once per session but authorized thousands of times within it.
Why the distinction matters
Blurring the two concepts produces real vulnerabilities. A system that authenticates users but authorizes poorly lets any logged-in person reach any data, which is how many API breaches involving insecure direct object references happen. A system with strict authorization but weak authentication is equally exposed, because an attacker with a stolen password inherits all of the victim's carefully scoped permissions.
The distinction also maps to different tools and standards. Authentication is strengthened with MFA, passwordless methods, and protocols such as SAML and OpenID Connect. Authorization is expressed through models such as role-based access control (RBAC) and attribute-based access control (ABAC), and enforced by policy engines. Compliance frameworks routinely ask organizations to demonstrate both: that identities are verified strongly and that access is limited to what each role requires.
Getting both right in practice
On the authentication side, centralize sign-in at an identity provider, require MFA, and prefer phishing-resistant factors such as passkeys for sensitive roles. On the authorization side, define roles from job functions rather than copying an existing user's permissions, review entitlements periodically, and default to least privilege so new access must be justified rather than removed later.
The two disciplines meet in the token: after authentication, the identity provider issues assertions carrying the attributes and group claims that applications use for their authorization decisions. Keeping those claims accurate through directory sync and automated provisioning is what makes the whole chain trustworthy. Monosign handles the authentication half with MFA options including TOTP, push approval, and passkeys, and feeds authorization with role and group claims delivered over SAML, OIDC, and SCIM.