User identification and authentication are absolutely essential to modern security. Mechanics of User Identification and Authentication presents the general philosophy of user authentication and access control. Introducing key concepts, this text outlines the process of controlled access to resources through authentication, authorization, and accounting. It provides specific information on the user authentication process for both UNIX and Windows. Addressing more advanced applications and services, the author presents common security models such as GSSAPI and discusses authentication architecture. Each method is presented with a specific authentication scenario.