In a previous post we’ve covered how to create encrypted disk images on your Mac. Another way of achieving some level of security is to add encryption to a USB drive, either an external hard disk or a USB key (thumb drive).
After the setup is done, each time you connect the USB drive OS X will prompt you to enter the master password for the disk.
There is a gottcha with this, the disk will only work on OS X, you can’t use the drive to plugin to a Windows machine.
Setup the Encryption
It’s worth stating: this is going to destroy all of the data on the disk, so ensure you’re fine with that before you begin.
On your Mac, in Spotlight, search for Disk Utility and run it.
Select the disk that you’d like to work with, then click the Erase tab along the top of that screen. Here you need to choose the format for the disk, from the drop down menu choose Mac OS Extended (Journaled, Encrypted) – See the screen shot below.
Now click the Erase button bottom right. You will now be prompted to enter a master password for the disk. Don’t forget this one as without it your data is not able to be accessed.
After a few moments the job is done.
Now if you unplug and then reconnect the disk, you’ll find that OS X will prompt you for a password before the disk is mounted.