Understanding Authentication vs Authorization

Authentication verifies the identity of users, answering the question "Who are you?", while authorization determines what authenticated users can do, answering "What are you allowed to access?". These concepts are often confused but must be implemented as separate layers in your security architecture. Authentication typically involves credentials like passwords, biometric data, or cryptographic tokens, while authorization involves checking permissions, roles, or access control lists. Both must be implemented correctly to maintain application security.

In modern web applications, authentication often spans multiple layers: initial login, session management, API authentication, and service-to-service authentication. Each layer requires different security considerations and implementation patterns. Similarly, authorization can range from simple role checks to complex attribute-based access control (ABAC) systems. Understanding these distinctions helps developers choose appropriate patterns for their specific use cases.