In one embodiment the BCU 103 may associate one unique “active” key pair Kpv/Kpb with an authorized user 101 of the PID 100, which key pair Kpv/Kpb may be updated by the BCU 103 from {HEAD ~ time} to {TAIL ~ time}, thereby replacing the previous key pair 
to
In one embodiment the BCU 103 may associate one unique “ active ” key pair Kpv / Kpb with an authorized user 101 of the PID 100 , which key pair Kpv / Kpb may be updated by the BCU 103 from { HEAD ~ time } to { TAIL ~ time } , thereby replacing the previous key pair
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