Using Disk Utility To Protect Important Files

Need an easy to protect some important documents or files? We've covered securing your home folder in Mac OS X using FileVault but this won't cover you if you are storing data outside that location. A great example of this is offsite storage.

Let's say you have some financial records on your computer. You keep them safe on your Mac but you want to keep a copy someplace else in the event your hard drive fails or (worse) you lose your home in a disaster. Be it a USB flash drive kept at a friend's house or your trusty iDisk, there is a way to keep those important files safe from prying eyes. The best part? You can do it with tools built right into Mac OS X.

To do this, open the Utilities folder under Applications. Next, open Disk Utility.app. This is where the fun begins.

On the top of the Disk Utility application, click the New Image button. A window will drop down with several options. This process will create a DMG (Disk Image) file that you can mount on any Mac and drop files into. You are probably familiar with DMG files as they are commonly used to package OS X applications that you download from the Internet. Unlike those, however, we are going to encrypt ours.

On the top, next to Save As, give it a name. This is the name of the DMG file. You can call it anything you'd like. On the lower part of the window you are asked to provide a Volume Name. Again, this is up to you. Next you can choose a volume size. Make sure you make it big enough to fit all the files you want to protect but don't make it too large as you'll just end up wasting space. You can leave the Volume Format alone. Unless you know what you are doing, there's no need to change this.

Finally, choose an option under Encryption. 128-Bit AES Encryption is pretty secure, however, if you want to feel really secure about your data, you can opt for the stronger 256-bit AES. When you have made your choice, click the Create button. 

When the encryption process begins, you'll be asked to provide a password. You know the drill: Make it easy for you to remember but hard for others to figure out. Disk Utility even offers you a security gauge as you type so you know you've made a good one. Make sure you remember this password! If you forget it, all of the data stored inside this DMG file will be inaccessible.

You now have a secure disk image that you can use to protect important files, no matter where you store it. When you open the DMG file and enter the password, it will mount the disk right on your desktop so you can treat it like any other storage device. Once you "eject" it, your files are protected from prying eyes. Couldn't be easier!