OS X Mountain Lion: Recovery key
If you’ve encrypted your disk with FileVault full disk encryption and you forget your password, your information is not accessible and is essentially lost. To provide some protection against losing your data, a recovery key is created when you turn on FileVault. The recovery key can be used to unlock your encrypted disk and reset your login password.
Copy your recovery key and keep it in a safe place. Don’t keep the recovery key with your computer where it can be discovered by others. Don’t store it on your computer. The key is encrypted with all your other information, and it is therefore inaccessible.
As a further precaution against losing your recovery key, you can store it with Apple. When you choose this option, you pick three security questions. Then if you forget your recovery key, you can contact Apple Support, provide the answers to these questions, and retrieve your recovery key.
If you get a message stating “A recovery key has been set by your company, school, or institution,” it signifies that the administrator for your organization has created a recovery key for this computer. If you forget your password and need to unlock your encrypted disk, contact your administrator to unlock your disk with the administrative recovery key, you will then be able to reset your password.