Encrypted Swap

Install loop-aes
$ sudo apt-get install loop-aes

list swap partitions
$ swapon -s

Modify fstab
$ sudo vi /etc/fstab

before:

/dev/hda2 none swap sw 0 0

after:

/dev/hda2 none swap sw,loop=/dev/loop7,encryption=AES256 0 0

Now either reboot so that the system picks up the changes, or:

turn swap off
$ sudo swapoff -a

turn swap back on
$ sudo swapon -a