Motorola Corporation

Kevin Gardeck

Kevin M Cutts

David A Green

A method of providing over the air rekeying information to roaming communication units in a secure wide area communications system including a home key unit 101, a first key unit 102, and second key unit 103 operably linked together. A communication unit 104 affiliated to the home key unit 101 roams to the locality of the first key unit 102. The roaming communication unit then transmits a key request 112 to the first key unit 102 that transmits a unit information request 108 to the home key unit 101. The home key unit 101 responds by transmitting a rekey information packet 109, that includes a unit key 110, to the first key unit 102. The first key unit 102 then transmits a key information packet 113, that includes the unit key 110, to the roaming communication unit. The roaming communication unit then uses the unit key 110 to communicate securely at the locality of the first key unit.

Method of rekeying roaming communication units

In a secure communication system 100, communication units in different communication groups may be simultaneously rekeyed over the air by having a managing key unit 101 generate a key packet 121. This key packet 121, which includes a unit key 122, a key alias 123, and a key representation 125, is transported to at least one fleet key unit 102. Upon receiving the key packet 121, the fleet key unit determines, based on the key alias, which communication units of which communication groups are to be rekeyed. Once this is determined, the key representation 125, which represents the unit key (encryption key) 122, is transmitted to the communication units, thus rekeying multiple communication units in multiple communication groups simultaneously.

Method for over the air rekeying of multiple communication groups

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.

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Algonquin, IL, United States of America

Kevin Gardeck