Abstract
In this paper, a group-mobile radio system with private communication capability is proposed. The dispatch radio systems are attractive because of their capability of featuring group calls via the working channels. When a group call is initiated, messages originating from a mobile unit are addressed to the intended group via a dispatch center which administrates the activities among the mobile units. Due to the fact that the make-up in mobile units in the dispatch radio system are organized as a hierarchy, the message exchanges are usually group communications, so that group calls become the main concern in real applications. In this paper, a cryptographic mechanism is utilized to achieve private communication during the message exchanges. Moreover, not only can our scheme provide secure message sharing among the intended mobiles, but it is also possible for the message to be monitored by the leader of the mobiles group. The computing time in our scheme remains acceptable providing a high-speed processor is installed in the mobile unit. © 2004 Taylor & Francis Group, LLC.