Authentication servers are essential components in digital security, serving as dedicated systems that verify user identities before granting access to websites or applications. They act as intermediaries between application servers and clients, ensuring that only authenticated users can access sensitive information. Typically, these servers use protocols like OAuth 2.0, Password Authentication Protocol (PAP), Challenge-Handshake Authentication Protocol (CHAP), Extensible Authentication Protocol (EAP), and Lightweight Directory Access Protocol (LDAP) to validate credentials. They support both stateful and stateless authentication methods, with the latter preferred for its scalability and simplicity. By centralizing authentication processes, these servers facilitate scalability, simplify management, and enable features like Single Sign-On (SSO), thereby enhancing security and efficiency. Once authentication is completed, the process often transitions to authorization, determining the specific resources a user can access.