Opencrypt can use 0, 1 or 2 keys, dispatched on different devices and/or servers on a network, to open automatically during boot the crypted partitions. Keys can be the same or different for each partition to open.
For each partition opencrypt will first try to find keys on unencrypted devices (USB stick, etc). Opencrypt will then search missing keys on network. If the partition could not be opened, opencrypt will ask a password on keyboard.
If you have any questions please contact us at debian@verdier.eu.