Encrypt Your USB Flash Drives, External USB Drives Or SD Cards [OS X Tips]

Encrypt Your USB Flash Drives, External USB Drives Or SD Cards [OS X Tips]
Encrypt Your USB Flash Drives, External USB Drives Or SD Cards [OS X Tips]

Mac OS  X Lion introduced the world to FileVault 2 Apple’s solution to full disk encryption. It is one of my favorite features in Lion, and it is definitely a welcome addition to Mac OS X. Just about anyone can use it to encrypt the startup disk on their Mac, but more importantly, they can use it to encrypt their USB thumb drives and SD cards. Why is that important?

It is important because USB thumb drives and SD cards are small and easily lost. If they are encrypted, you don’t have to worry about whether the content they carry falls into the wrong hands.

Before we start, a very important thing to know is you should not do this on any of these devices that contain data you want to keep, since your USB thumbdrive or SD card will be completely erased. If you must use a particular device with data on it, you’ll need to copy or back up that data to another drive first, then copy it back later.

The first thing you need to do is insert the USB thumb drive or SD card into your Mac. Afterwards, find the Disk Utility app in the /Applications/Utility folder on your startup drive and launch it. You’ll see something like this:

Encrypt Your USB Flash Drives, External USB Drives Or SD Cards [OS X Tips]

In the example above, I’ve selected a USB thumb drive by clicking on it in Disk Utility. Once selected, I then clicked on the Erase tab.

Encrypt Your USB Flash Drives, External USB Drives Or SD Cards [OS X Tips]

I changed the format type to Mac OS X Extended (Journaled, Encrypted) using the drop down as shown above. Then I entered a name, but I could have accepted the default — Untitled.

Click the Erase button to completely erase and encrypt the device using FileVault 2. You’ll be prompted to enter a password before the drive is actually formatted.  Once you do so, the process begins. Be sure you aren’t using something with data on it you care about.  In a few minutes or less you’ll have an encrypted blank drive or SD card ready for you to use, but with a few caveats:

  • It  is only compatible with a Mac running Mac OS X Lion.
  • It is not compatible with Windows or any other operating system.
  • You’ll need the password you selected in Disk Utility to mount and use the drive on your Mac. If you loose the password you won’t have access to the data on the drive or SD card.

Although there are some limitations, the trade offs are reasonable if you are concerned about protecting your data and if you are worried about losing something as small as an SD card or thumb drive.

Finally, there is one other positive thing to mention about FileVault 2 encryption. It will also work with external drives attached via USB, Firewire, and Thunderbolt using the same steps above.

  • djgrahamj

    One solution to the Lion-only problem is to format the drive unencrypted then create an encrypted DMG on it. This way you get backwards compatibility with previous OSX versions.

  • freedommcflyy

    This is a great tip, I have been looking for something like this for a long time. Keep the great posts coming!

About the author

David W. MartinDavid W. Martin has more than 20 years of experience in the industry as a programmer, systems and business analyst, author, and consultant. David has written for CNET's iPhoneatlas.com, MacLife.com, CultofMac.com, BYTE.com and recently for aNewDoman.net. He comes to Cult of Mac's website with deep knowledge and passion for the all things Apple. Follow David on Twitter @david_w_martin or see what he's up to now at davidwmartin.com.

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