An authenticator is a way to prove to a computer system that you really are who you are (called authentication

Authentication

Authentication is the act of confirming the truth of an attribute of a datum or entity...

). It is either:

• A piece of data (often called a token) that you got from the last place where you proved who you are (to save you, or the software, the hassle of logging in again).
• A program, usually running somewhere on the computer network, that takes care of authentication.

Authenticator tokens are common when one program needs to authenticate itself to a larger server

Server (computing)

In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...

 or cloud

Cloud computing

Cloud computing is the delivery of computing as a service rather than a product, whereby shared resources, software, and information are provided to computers and other devices as a utility over a network ....

 repeatedly. For instance, you (the human) might sign on to a secure website with your name and password

Password

A password is a secret word or string of characters that is used for authentication, to prove identity or gain access to a resource . The password should be kept secret from those not allowed access....

, after which you can surf around inside the secure server, visiting different web pages. Every time you move to a new page, however, the server must believe that you are the same person who originally signed in (otherwise it will refuse). Your browser keeps an authenticator token, which it sends upon every page request (often as a browser cookie

HTTP cookie

A cookie, also known as an HTTP cookie, web cookie, or browser cookie, is used for an origin website to send state information to a user's browser and for the browser to return the state information to the origin site...

), that does this.

More complex situations might involve a program that runs automatically (say, at 4:00am every morning) that similarly requires authentication to get at the data it needs, but there's no human around to log in for them. An authenticator token must be prepared in advance that this program uses. Ultimately, some human must authenticate to create such a token.

• In INFOSEC, authenticators are means used to confirm the identity or eligibility of a station, originator, or individual.
• In IEEE 802.1X
  IEEE 802.1X
  IEEE 802.1X is an IEEE Standard for port-based Network Access Control . It is part of the IEEE 802.1 group of networking protocols. It provides an authentication mechanism to devices wishing to attach to a LAN or WLAN....
  
  , an authenticator is an entity at one end of a point-to-point LAN segment that facilitates authentication of the entity attached to the other end of that link. In practice, the authenticator is usually a network switch
  Network switch
  A network switch or switching hub is a computer networking device that connects network segments.The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI model...
  
   or wireless access point
  Wireless access point
  In computer networking, a wireless access point is a device that allows wireless devices to connect to a wired network using Wi-Fi, Bluetooth or related standards...
  
   that serves as the point of connection for computers joining the network. The authenticator receives connection requests from a supplicant
  Supplicant (computer)
  The term supplicant is used in the IEEE 802.1X standard, where the supplicant is an entity at one end of a point-to-point LAN segment that seeks to be authenticated by an authenticator attached to the other end of that link. In practice, a supplicant is a software application installed on an...
  
  on the connecting computer.