Communication system, communication unit and method for dynamically changing an encryption key

摘要

A method to dynamically change an encryption key in a wireless communication system that employs an encryption protocol is described. The communication system includes a serving communication unit communicating with a plurality of remote communication units. The method comprises the steps of: communicating a message, from the serving communication unit to the plurality of remote communication units wherein the message includes an indication of a communication resource for the plurality of communication units to use and notifying the plurality of remote communication units of a change in an encryption key or encryption mode, within said message. This eliminates conditions of corrupted circuit mode speech or data as a result of a key change during a call, thereby minimising loss of service and disruption to the end-user(s). Furthermore, it provides a reliable mechanism to change the AI cipher key or encryption mode of a communications channel that is assigned for use in circuit mode speech or data. <IMAGE>