Method for authentication and protection of subscribers in telecommunications systems
 A method and apparatus for authentication between a subscriber unit and a communication unit is provided. The authentication process includes: maintaining an historic non-arbitrary value in the subscriber unit, generating an authentication message in the subscriber unit as a function of at least part of the historic non-arbitrary value, and transmitting the authentication message to the communication unit. In addition, the authentication process includes: receiving an authentication message at a communication unit, maintaining an historic non-arbitrary value in the communication unit, and determining, in the communication unit, through the use of the received authentication message and the maintained historic non-arbitrary value, whether a received service request is authentic. In another embodiment, the authentication process includes: providing the subscriber unit with at least part of a plurality of dialed digits which uniquely identify a target communication unit, generating an authentication message in the subscriber unit as a function of the at least part of the plurality of dialed digits, and transmitting the authentication message and the at least part of the plurality of dialed digits from the subscriber unit to the communication unit. In addition the other embodiment authentication process includes: receiving an authentication message and at least part of a plurality of dialed digits which uniquely identifies a target communication unit, the authentication message being derived from the received dialed digits, and determining in the communication unit, through the use of the received authentication message and the received dialed digits, whether a received service request is authentic. 
Motorola, Inc.
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Mary B. Louis D. Larry C.
Flanders Finkelstein Puhl