Importance

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Abstract

A key update system uses information in an update message from a communications system to generate a new key and perform a bidirectional validation of the new key. After a unit validates the new key, at least a portion of information from the update message is used by the communications system to validate the new key. As a result, the communications system is not required to generate and transmit a separate authentication challenge to validate the new key. For example, a wireless communications system can send an update message with a sequence RANDSSD to the wireless unit. The wireless unit generates a new SSD using at least a portion of the sequence RANDSSD, and the wireless unit uses at least a portion of the new SSD to generate a signature value AUTHBS to validate the new key and thereby the home authentication center that initiated the update of the SSD. After the wireless unit validates the new key by comparing the AUTHBS generated by the wireless unit with an AUTHBS generated by the wireless communications system, the wireless unit uses at least a portion of the sequence RANDSSD and at least a portion of the new SSD to generate the validation value AUTHSSD. The validation value AUTHSSD can be sent to the wireless communications system along with a confirmation signal indicating the wireless unit has validated the new key. The wireless communications system can validate the new SSD by comparing the validation value AUTHSSD received from the wireless unit with a validation value generated in the same fashion by the wireless communications system.

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First Claim