Start up a terminal window and then enter the commands as shown in italics below. The following command will tell you if your swap is encrypted in Ubuntu 12.04.
swapon --summary <enter>
Filename Type Size Used Priority /dev/mapper/cryptswap1 partition 3904508 0 -1
Above indicates swap is encrypted. If it returned nothing except the heading, then swap is either non-existent or not encrypted.
sudo blkid | grep swap <enter>
If it returns something like:
/dev/mapper/cryptswap1: UUID=”a42948452-111a-4235-b24a-54752c21ecfe6″ TYPE=”swap”
then the swap partition is encrypted.
You can also check with:
cat /etc/crypttab <enter>
It would return a line as:
cryptswap1 /dev/sda10 none luks
This also indicates that the swap partition is encrypted.
sudo cryptsetup status cryptswap1 <enter>
/dev/mapper/cryptswap1 is active and is in use.
keysize: 256 bits
indicating that the swap is encrypted and is on partition /dev/sda10.
If you need to encrypt your swap partition after installation, then see how to encrypt swap partition.