[ Thanks to Mike
Weber for this link. ]
“The encryption is done using dm-crypt/LUKS. LUKS or Linux
Unified Key Setup, provides the disk format for the data as well as
it provides the passphrase/key management policy. LUKS uses the
dm-crypt module which is a kernel mapper subsystem and manages the
encryption and decryption for the block device. This is the same
subsystem that is used by LVM so that it has proven itself to be
stable. One of the advantages of LUKS is that the underlying
contents of the block device are arbitrary so that you can encrypt
your SWAP space. You can encrypt ext3, LVM physical volumes, and
RAID arrays with LUKS. A disadvantage of LUKS is that it is not a
good choice for file level encryption.”