Abstract: A method for authenticating a cellular service provider during over the air activation of a mobile station includes the steps of programming an A-key value into the mobile station and providing the A-key value to the service provider. The mobile station requests over the air activation by transmitting a registration request to the service provider. The service provider verifies billing information and generates two random numbers. The service provider then performs a first CAVE algorithm using the provided A-key value and the first random number to generate a first shared secret data value. The service provider performs a second CAVE algorithm using the first shared secret data value and the second random number to produce a first authentication value. The service provider then transmits the first and second random numbers along with the authentication value to the mobile station.