text: While the system enables encryption, you are prompted to insert USB flash drives into the 
  system. The system generates and copies the encryption keys to all available USB flash 
  drives. 
  
  Ensure that each copy of the encryption key is valid before you write any user data to the 
  system. The system validates any key material on a USB flash drive when it is inserted into 
  the canister. If the key material is not valid, the system logs an error. If the USB flash drive is 
  unusable or fails, the system does not display it as output. Figure 12-26 on page 625 shows 
  an example where the system detected and validated three USB flash drives. 
  
  If your system is in a secure location with controlled access, one USB flash drive for each 
  canister can remain inserted in the system. If a risk of unauthorized access exists, all USB 
  flash drives with the master access keys must be removed from the system and stored in a 
  secure place. 
  
  Securely store all copies of the encryption key. For example, any USB flash drives that are 
  holding an encryption key copy that are not left plugged into the system can be locked in a 
  safe. Similar precautions must be taken to protect any other copies of the encryption key that 
  are stored on other media. 