Authentication Before networks, the task of validating the identity of a particular user was simple. A terminal and timesharing computer were able to assume that whoever was currently typing at the keyboard had the same identity as the session initiator. The system of account names, verified by a password at startup time was easily enforced. Today, computers requesting and providing services over networks are not secure. A network authentication service is needed to act as a secure third party between non-secure hosts on the network askingfor services, and hosts providing the services.
Many people require access to multiple computer systems.
They can end up with a long list of accounts and passwords. Most people cannot effectively keep track of multiple accounts and passwords, especially when they differ across platforms. Single Signon represents the concept that a computer user can be authenticated once, and for the rest of their session, any other systems or networks connected to would check with a security database to determine privileges, with no need for any further signons, interruptions, or passwords. Effective implementation of Single Signon requires a mechanism that combines user authentication and authorization. Authorization is the process of determining whether a client may use a service, which objects the client is allowed to access, and the type of access allowed for each.