Method and apparatus for authentication in a communication system

A method and apparatus for identifying a mobile subscriber. In the preferred embodiment, the subscriber receives a challenge in the format in the local acknowledgment protocol and determines whether the local acknowledgment protocol is the subscriber's home system acknowledgment protocol. If it is not the subscriber's home system identification protocol, the subscriber converts the challenge into a format (eg bit length) suitable for that home system identification protocol, and treats the translated challenge with the subscriber's secret key and verification algorithm as an acknowledgment. do. The acknowledgment is converted to conform to the local acknowledgment protocol and transmitted to the local system communication device. The challenge and response are forwarded to the subscriber's home system with similar transformation and processing, and the subscriber's response is compared with the home system generated response.