How to encrypt external devices?

Solution 1:

Linux platform only

You can use the disk utility that comes installed with Ubuntu by default.

Install the cryptsetup package: sudo apt-get install cryptsetup

If the gnome-disk-utility package is not installed: sudo apt-get install gnome-disk-utility

Some things to have in mind prior:

Any data that is on the partition will get erased
This is NOT suitable for a partition that is running your current OS
Again, back up everything and be sure to format the correct drive!

Creating a new encrypted partition:

Start the Disk Utility:

Make sure you identify the proper drive in the left hand panel.
If needed, create empty space on the disk by resizing/deleting partitions.
In the Volumes graphic overview, click the appropriate empty block.
Click Create partition to create the partition to be encrypted.
Check Encrypt underlying device.

They will then prompt you for a password. Chose a decent password - your encryption will only be as strong as your password. It is probably also safer not to store the password, choose the option Forget password immediately.

Encrypting an existing partition

Select the partition that you want to get encrypted
Make sure that it is not mounted by pressing on the "stop" button
Click the "gear" icon under the partition and choose Format...
Select the type Encrypted, compatible with Linux systems (LUKS + Ext4)
Enter a name to distinguish the partition
Enter your passphrase to encrypt it and confirm it

For higher security, if you have have any existing data in this partition, select the erase option. You can overwrite existing data with zeroes, but this could take several hours depending on the disk.
Format it and wait until it finish in a couple of minutes!

Using your encrypted partition

Once your partition is formatted, it will be encrypted.
In fact, you have two partitions, a container partition and the encrypted partition.
Disk Utility will show them above each other when the volume is unlocked.
From the Disk Utility, you can lock and unlock the volume by selecting the partition with the little lock and clicking Lock Volume or Unlock Volume.

Make sure that you leave it closed/locked before unmounting the system, otherwise you will get an error. Also, with two partitions, you will have to unmount both before being able to safely remove the drive.

In the Disk Utility, there also is a button Change passphrase, which works much faster than the initial formatting.

From Nautilus, you can mount and unmount the encrypted volume almost like a normal external USB drive or memory stick, except that you will be prompted for the password.

Source: https://help.ubuntu.com/community/EncryptedFilesystemsOnRemovableStorage

Solution 2:

CLI

cryptsetup -v --verify-passphrase luksFormat $1   # Answer YES in CAPITAL - case matters!
cryptsetup luksOpen $1 backup
mkfs.ext4 /dev/mapper/backup
cryptsetup luksClose /dev/mapper/backup

where $1 is the partition address (/dev/sdc1 for example)