Encrypting a USB Drive on a Mac Made Easy
Mac OS 10.11.x “El Capitan” Edition

(NOTE: This was written for OS X 10.11.5 “El Capitan.” If you’re looking for the later entry for macOS 10.12.x “Sierra,” click here. For the YouTube video for Sierra edition, click here. The original blog entry written for OS X 10.9 “Mavericks” can be found here)

Like many of my clients and friends, I use a flash drive (also known as a “USB drive” or “Pen drive” or “Thumb drive” etc.), for backing up important files. One of the things I’ve noticed, though, is how many people put sensitive and personal data on these flash drives but don’t even bother to encrypt them. The reason it’s important to encrypt these flash drives is because these flash drives are usually physically small and can be easily misplaced, lost or stolen. If they are encrypted, you don’t have to worry about the data on them being accessible to someone that may have stolen your flash drive or happened to have found it lying around somewhere.

Apple’s Mac OS X 10.7 “Lion” and later operating systems make it easy to do a full disk encryption of these flash drives. You can also easily encrypt Secure Digital “SD” cards and Micro-SD cards too! SD cards are typically what is used in digital cameras to record the images taken with the camera. Most Macs have built-in SD card slots so Apple has made SD cards very easy and convenient to use.

In order to encrypt a flash drive or SD card (we’ll call them “media” collectively from this point onward), you should either start with brand new media or prepare to reformat the media that you may already have. If your Mac has USB 3.0 ports (most Macs since 2012), you should use USB 3.0 compatible media for this project as on-the-fly encryption can slow down reading and writing to an external drive. Please note that when you reformat this media, you are effectively erasing it so any existing data (e.g. files, folders, programs, etc.) will be lost! If you’re using existing media, you should consider copying or backing up the data on that media to another media first so that you can then copy it back to the encrypted media later. All media seem to come from the factory formatted as FAT32 (a holdover from the old MS-DOS & Windows ’95 era) as this is a disk format that nearly all personal computers, whether they be Mac, Windows, or Linux, can read and write. To encrypt your media, however, you’ll need to format it in a Mac specific format called, “GUID Partition Map.” In other words, you cannot easily create an encrypted disk on the Mac without first having changing the format of the drive from FAT32 to GUID.

The first thing you need to do is insert the media into your Mac. Afterwards, go to your Mac’s Applications folder and locate the Utilities folder. Inside the Utilities folder, you’ll find the Disk Utility application. Double-click on its icon to launch it. Disk Utility will show you a list of all internal and external drives connected to your Mac.

In the screenshot above, I’ve selected my flash drive by clicking on it once in Disk Utility (in my example, it’s called, “Lexar USB Flash Drive” in the left-hand column under the “External” column heading. Once selected, I then clicked on the Erase tab. I then changed the format type to “Mac OS X Extended (Journaled)” using the drop down box as shown in screenshot. At this point, you can type in a name for your media (where it says, “Give Drive a Name” ). Naming your media can help you keep your media organized. After all, most of us have several of media, right? Giving them names helps us keep them straight! Once the formatting process is complete, your screen should look like the screenshot below:

Next, you want to find your media on your Mac’s Desktop and right-click it (or hold down and click on it) and choose “Encrypt [your media’s name here].”

Next, the Mac will prompt you to enter an encryption password before it begins the process of encrypting your media. Please remember to use a password that is not only hard for someone to figure out but one that you can easily remember. Please also note that if you cannot remember the password you used when formatting and encrypting the media, then you will not be able to access the data contained on that media. You will also be given the opportunity to give yourself a “hint” on what the password is. I’d recommend writing a hint that you can figure out but would be meaningless to someone who doesn’t know you.

In a minute or two, you’ll have an encrypted flash drive or SD card ready for you to use! Remember to always drag your media off your Mac’s Desktop to your Trash to eject it properly. This step helps to prevent data loss that can result by simply pulling the media out of your Mac.

When encrypted media is plugged into your Mac, you will be prompted to enter the password you selected in order to access the data on that media. If you cannot remember your password, you can click on “Show Hint” and any hint you may have established while setting up the encrypted media will be displayed to assist you in remembering what the password is. Personally, I’d recommend that you not have the password remembered in the keychain (call/email/text me as to why!).

While Apple’s Disk Utility program is easy to use, there are a few drawbacks to using it to create encrypted media:

• The encrypted media can only be accessed with a Mac running Mac OS X “Lion” or later. Provided you know the password, you will be able to access the media and the data on it with any Mac running Mac OS X “Lion” (10.7), “Mountain Lion” (10.8) and “Mavericks” (10.9), “Yosemite” (10.10), and “El Capitán (10.11).”
• The media is not compatible with Windows or any other operating system (i.e. Windows or other operating systems will not be able to access the data contained on the media). Most flash media come pre-formatted for use with PCs running Windows but your Mac can also access them. This process will make your media Mac only. It’s not a big deal unless you live or work in a mixed computing environment containing Macs and PCs.
• As mentioned above, you’ll need the password you selected in Disk Utility to mount and use the media on your Mac. Without it, the data on the media cannot be accessed.

Tags: encrypt drive pen flash thumb , mac, 10.11, el capitan