With TrueCrypt drives and disk- images can be encrypted on Mac OS X. Unlike the native disk utility program TrueCrypt can be used to encrypt disk drives and disk images not only on Mac OS X but also under Windows and Linux.
Another advantage over the disk utility program is option to create hidden drives. After installing, the integrated Wizard can create step by step encrypted disks and images.
For encryption there can be assigned a password or a password file, but the drive cannot be decrypted without this file.