Here’s a tip for easily creating encrypted Disk Images, which are used to store sensitive files on your Mac. I thought of this Mac Treat as I began to scan my 2008 tax documents onto my MacBook Pro. I want to password-protect these documents, since they contain many personal details, such as my social security number, address, etc. If someone stole my MacBook Pro and was able to get past my Mac’s login password, they’d have everything needed to steal my identity. Of course, maybe they’d be doing me a favor by stealing my identity, but still.
A “Disk Image”:http://en.wikipedia.org/wiki/Apple_Disk_Image can be thought of as a special folder that allows both file compression along with the option for password protection. A Disk Image is often used to distribute software over the internet. When you open a Disk Image, it is “mounted” as a drive within the Finder, and shows up as a drive on your Mac’s desktop. Disk Images have the .dmg extension.
I used OS 10.5 for this article, but this should work just the same for 10.3, 10.4, and even 10.2.
1. Launch Disk Utility, which is typically located in your Mac’s Application Folder.
2. Click on the “New Image” button, or navigate to the menu bar at the top of the screen and choose File > New > Blank Disk Image
3. In the new window that opens, name the new Disk Image (under Save As), then choose a Volume Size (I usually choose 610MB so I can burn the image to CD; you can choose a Disk Image as large as 8GB for dual-layer DVDs).
4. Next, choose your encryption. I always use 128-AES encryption. If you don’t choose encryption here, your image won’t be encrypted.
5. Finally, choose “sparse Disk Image” under Image Format. I leave the other options fixed on their default settings.
6. Click “Create” or “OK” (depending on the OS you’re using).
7. In the new window that opens, enter a strong password. Make sure to deselect the “Remember Password” option. If you need help choosing a password, click the image of the key to launch the Password Assistant application.
*Don’t forget this password, because there is no way to open the image without it.*
8. Quit Disk Utility and navigate to your Mac’s desktop, where you’ll see two new files – the Disk Image where you stash your files (in 10.5, typically an icon that looks like a white CD drive) and the Disk Image installer (which typically looks like a hard drive icon).
9. Test your new Disk Image by double-clicking it and supplying the password (note that if you selected “remember password” above, you won’t be prompted to enter the password). Add a few files.
Next, to continue testing the Disk Image, drag the mounted Disk Image into the Trash to eject it. Leave the Disk Image installer that looks like a hard drive icon on your desktop. When the Disk Image is ejected, double click on the Disk Image installer to re-mount the Disk Image. Enter your password and make sure your files are all there.
??Note: files added to your encrypted Disk Image are copies of the original files. The original files will continue to exist on your Mac until you delete them. Don’t delete any files until you’re sure they’ve been copied into the encrypted Disk Image.??
10. So long as everything works, you can now use the Disk Image just like you’d use any other folder or flash key. You can move the Disk Image into your Mac’s Documents folder, or even onto a real flash key.
Also, make sure to back up this encrypted Disk Image, so your important files won’t be lost if your computer is stolen or suffers irreparable harm!
