Lifehacker: The Guide to Working Smarter, Faster, and Better, Third Edition

Hack 21: Create a Password-Protected Disk on Your Mac

Level. Medium

Platform Mac OS X (10.4 or later)

Cost Free

If you have files and folders you’d like to keep private and secure on your Mac, you can use Mac OS X’s built-in Disk Utility to encrypt a disk image. A disk image is just a file that you can mount like a separate disk and unmount to lock again — like a thumb drive, but without the actual physical drive. Whether you want to password-protect sensitive customer data or your spouse’s surprise birthday party plans, an encrypted disk image can lock up any number of files and folders behind a password. This hack covers how to lock and unlock a disk image.

Create a New Encrypted Disk Image

Here’s how to create an encrypted disk image:

1. Launch Disk Utility, located in /Applications/Utilities/.

2. From the File menu, choose New ⇒ Blank Disk Image.

3. Enter a name (my-secret-files, for example) for your disk in the Save As dialog. From the Size drop-down list, choose how big you’d like the disk to be. (Make it large enough to accommodate all the data you want to store there.) From the Encryption drop-down list, select 128-Bit AES Encryption (Recommended), as shown in Figure 2-18.

Figure 2-18: Set the name, size, and encryption for your new password-protected disk image.

4. Next, you set a password to access the disk image. Make your password both secure and memorable. (For ...