============================================================================ SUBJECT: METHOD FOR UPDATING ENCRYPTION KEY INFORMATION IN COMMUNICATION UNITS SOURCE: MicroPatent via Fulfillment by INDIVIDUAL, Inc. DATE: July 6, 1994 INDEX: [2] ORDER NO: 402693# ---------------------------------------------------------------------------- MicroPatent via INDIVIDUAL, Inc. : Abstract: Within a communication system, an encryption controller receives unit identification information from a plurality of encrypting/decrypting communication units. For any individual communication unit, the encryption controller uses the unit identification associated with that transmitting communication unit to determine if it contains updated encryption key information. If the transmitting communication unit is not currently updated, a group call is used to send the current encryption key information to all communication units within the transmitting communication unit's group, thereby updating all active, non-current communication units. After a first predetermined period of time has elapsed, this process is allowed to repeat. Ex Claim Text: In a communication system that includes a plurality of communication units, an encryption controller, wherein the plurality of communication units includes a first set of communication units that are currently active and a second set of communication units that are currently inactive and wherein communication units of the plurality of communication units readily change from the first set of communication units to the second set of communication units and vice versa, a method for updating encryption key information to the plurality of communication units, the method comprises the steps of: a) transmitting, by a first communication unit in the first set of communication units, unit identification information to the encryption controller; b) when the unit identification information is received, determining, by the encryption controller, that the first communication unit does not have updated encryption key information; c) transmitting, by the encryption controller, updated encryption key information to the plurality of communication units, wherein only the first set of communication units are updated with the updated encryption key information; d) initiating, by the encryption controller, a predetermined wait period; e) changing, by a second communication unit, from the second set of communication units to the first set of communication units; f) after expiration of the predetermined wait period, receiving, by the encryption controller, unit identification information from the second communication unit; and g) when the unit identification information from the second communication unit is received, retransmitting, by the encryption controller, the updated key information to the plurality of communication units, wherein communication units that have changed from the second set of communication units to the first set of communication units are updated with the updated encryption key information. Patent Number: 5325432 Issue Date: 1994 06 28 Assignee: Motorola, Inc. Inventor(s): Gardeck, KevinCutts, Kevin M. If you require additional information on this patent, please call PatentQuery at 800-984-9800. [07-06-94 at 18:24 EDT, Copyright 1994, MicroPatent, File: m0701215.4pa]