Method for improved authentication for cellular phone transmissions

An authentication process is triggered when a subscriber of a GSM-type cellular-phone-network service attempts a call. In this authentication process, an encrypted result, or a "signed response," previously stored in the subscriber's cellular phone, is transmitted to a Mobile Switching Center (MSC), and a Home Location Register (HLR) in the MSC compares the signed response to an encrypted result previously stored at an Authentication Center (AuC). If the signed response matches the stored encrypted result, the call is allowed to proceed; otherwise, access to a telephone network is denied. Proceeding with the call, the AuC generates a random number and derives a new encrypted result by means of a ciphering algorithm, e.g., a CAVE algorithm, using the random number and the subscriber's unique key previously stored in a database at the AuC. The new encrypted result replaces the previously-stored encrypted result, and the MSC transmits the new random number to the cellular phone, which independently derives a new signed response by means of a CAVE algorithm using the transmitted random number and the subscriber's unique key stored in a Subscriber Identity Module (SIM) for the cellular phone. The new signed response is then stored in the cellular phone.