How to Encrypt Time Machine Backup Data
January 2nd 2011Would you like to secure your Time Machine backup data so other people wouldn’t be able to view your files if your backup drive fell into the wrong hands? Apple doesn’t provide a built-in way to encrypt your Time Machine backup files but it can be done. A clever individual named Jay has figured out how to do it and has the best documentation that I could find on how to setup encrypted Time Machine backups. Thanks Jay.
In previous Tech Tips, I’ve written about how useful Time Machine can be as well as how to setup Time Machine and test your Time Machine backups. Apple got a lot of things when they created Time Machine. It’s by far the easiest backup system to setup, monitor and to use to restore a file. Having said that it does have some short-coming including the fact that it doesn’t let you automatically switch between multiple hard drives and it doesn’t let you encrypt your backup data. I describe how to manually switch between drives but Jay offers a way to automate the process. I haven’t tested his method myself but I have successfully setup encrypted Time Machine backups.
Jay provides excellent step-by-step setup instructions but here’s a quick overview.
You obviously need an external hard drive on which Time Machine will store the encrypted data. (Time Machine comes with Mac OS X 10.5 or newer.) Next, you use Disk Utility to create an appropriately named encrypted sparse bundle disk image which you put on the external hard drive. Save the password for your disk image and then move this saved password from your own Login keychain to the System keychain. The disk image then needs to be tweaked slightly so Time Machine will be able to figure out that it can store your data in it. This is accomplished by creating a custom preference (plist) file and putting this plist file into your Disk Image. Finally, select the external hard drive in Time Machine Preferences and Time Machine will magically store the backup data inside the disk image.


