Protecting Files with FileVault in Mac OS X Lion
If you absolutely, positively don’t ever want anyone to be able to access the files in your Mac OS X Lion Home folder, an application called FileVault allows you to encrypt your entire Home folder and its contents. In Lion, FileVault protects your data with the latest government-approved encryption standard: Advanced Encryption Standard with 128-bit keys (AES-128).
When you turn on FileVault, you’re asked to set a master password for the computer. After you do, you or any other administrator can use that master password if you forget your regular account login password.
If you turn on FileVault and then forget both your login password and your master password, you can’t log in to your account, and your data is lost forever. Really. So don’t forget both passwords, okay?
FileVault is useful primarily if you store sensitive information on your Mac. If you’re logged out of your user account and someone gets access to your Mac, there is no way they can access your data.
Because FileVault encrypts your Home folder, some tasks that normally access your Home folder might be prevented. For one thing, some backup programs won't work if FileVault is enabled. Also, if you’re not logged in to your user account, other users can’t access your Shared folder(s).
And because FileVault is always encrypting and decrypting files, it often slows your Mac when you add or save new files, and it takes extra time before it lets you log out, restart, or shut down.
To turn on FileVault, follow these steps:
Open the Security & Privacy System Preferences pane.
Click the FileVault tab.
Click the Turn on FileVault button to enable FileVault.
To turn off FileVault, click the Turn off FileVault button.