Systems and methods are described for authenticating users. One embodiment comprises a conversion system that includes a first interface, a processing system, and a second interface. The processing system receives a user ID and user credentials in a first protocol from a first communication device through the first interface. The processing system processes the user ID and a key to generate a computed password, and then derives credentials from the computed password. The processing system compares the user credentials to the derived credentials. If the user credentials and the derived credentials correspond, then the processing system authenticates the user. The processing system then generates new user credentials from the computed password according to a second protocol used by a second communication device, and transmits the user ID and the new user credentials to the second communication device through the second interface.