text: After at least three USB flash drives are detected, the system writes master access key to 
  each of the drives. Note that the system attempts to write the encryption key to any flash 
  drive it detects. Therefore, it is crucial to maintain physical security of the system during 
  this procedure. After the keys are successfully copied to at least three USB flash drives, 
  the system displays a window, as shown on Figure 12-53. 