This is accomplished by assigning a pre-defined ‘code-word’ to a device or text file that has a unique file type in which can only be read at the server, and must match the server at the time of login. A common example of implementation are Remote Service Authenticators (RSAs) where a server randomizes a number over a short time period, broadcasts it via cellular networks to a small, battery powered cellular SIM card inside a USB-sized FOB, to display that number to use as part of the login credentials to gain access to a network. While this isn’t exact code, the fundamentals are the following in this