In {TAIL ~ 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 {HEAD ~ the BCU} 103 from time to time, thereby replacing the previous key pair 
In { TAIL ~ 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 { HEAD ~ the BCU } 103 from time to time , thereby replacing the previous key pair
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