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Authentication server

Wikipedia contributorsAdapted for Fathomly · View authors
1 min read
Source updated August 17, 2025

An authentication server provides a network service that applications use to authenticate the credentials, usually account names and passwords, of their users. When a client submits a valid set of credentials, it receives a cryptographic ticket that it can subsequently use to access various services.

Authentication is used as the basis for authorization, which is the determination whether a privilege may be granted to a particular user or process, privacy, which keeps information from becoming known to non-participants, and non-repudiation, which is the inability to deny having done something that was authorized to be done based on the authentication.

Major authentication algorithms include passwords, Kerberos, and public key encryption.

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This article is adapted from the Wikipedia article “Authentication server”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.

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Related topics

TACACS

Terminal Access Controller Access-Control System refers to a family of related protocols handling remote authentication and related services for network access control through a centralized server. The original TACACS protocol, which dates back to 1984, was used for communicating with an authentication server, common in older UNIX networks including but not limited to the ARPANET, MILNET and BBNNET. It spawned related protocols: Extended TACACS (XTACACS) is a proprietary extension to TACACS introduced by Cisco Systems in 1990 without backwards compatibility to the original protocol.

RADIUS

Remote Authentication Dial-In User Service is a networking protocol that provides centralized authentication, authorization, and accounting (AAA) management for users who connect and use a network service. RADIUS was developed by Livingston Enterprises in 1991 as an access server authentication and accounting protocol.

Multi-factor authentication

Multi-factor authentication, also known as two-factor authentication (2FA), is an electronic authentication method in which a user is granted access to a website or application only after successfully presenting two or more distinct types of evidence (or factors) to an authentication mechanism. MFA protects personal data, which may include personal identification or financial assets, from being accessed by an unauthorized third party that may have been able to discover, for example, a single password.