Abstract: A method and system for dynamically authenticating an Internet Protocol (IP) client at a central device comprising a dynamic passcode generation means which is synced to an authentication system within or connected to the central device, the dynamic passcode generation means connected to or built into the IP client; wherein the dynamic passcode generation means periodically generates a passcode according to a preset schedule; the IP client automatically sends the periodically-generated passcode according to the preset schedule to the authentication system to authenticate the IP client; and upon authentication until the IP client is no longer authenticated, the authentication system allows a IP communications services to be provided by the central device.