I have found the following 2 minute video which shows how to encrypt a usb drive using ubuntu's disk utility app:
http://www.youtube.com/watch?v=J_g-W6hrkNA
My question is, is that method using dm-crypt, or some other technique for encrypting the drive?
Yes.
gnome-disc-utility (or palimpsest as it was once named) uses Linux Unified Key Setup which is a disk encryption specification. It is an enhanced version of cryptsetup, using dm-crypt as the disk encryption backend. From the 1st link:
Linux Unified Key Setup (LUKS)
Cryptsetup is a utility used to conveniently setup disk encryption based on dm-crypt kernel module. These include plain dm-crypt volumes, LUKS volumes, loop-AES and TrueCrypt compatible format. Project also includes veritysetup utility used to conveniently setup dm-verity block integrity checking kernel module.
LUKS Design
LUKS is the standard for Linux hard disk encryption. By providing a standard on-disk-format, it does not only facilitate compatibility among distributions, but also provides secure management of multiple user passwords. In contrast to existing solution, LUKS stores all setup necessary setup information in the partition header, enabling the user to transport or migrate his data seamlessly.
LUKS was designed according to TKS1, a template design developed in TKS1 for secure key setup. LUKS closely reassembles the structure recommended in the TKS1 paper, but also adds meta data for cipher setup management and LUKS also supports for multiple keys/passphrases.
