Accessing FileVault encrypted data from a hard drive removed from a Mac

Fixing this problem is predicated on you having either the user or master password to access the FileVault and sufficient disk space on the machine you are using to access the data from.

The problem: The logic board on my MacBook Pro (OS X 10.5.1) failed, leaving me with the cost of a repair as much as the cost of a replacement machine – so of course I bought the new machine. However, Apple’s FileVault does not allow access to FileVaulted data unless the hard drive is in the original machine. Moreover the new Macs cannot be ‘rolled back’ to earlier version operating systems, so I couldn’t even boot from the eternal drive. I tried booting from the install CD and re-installing OS X on the external (old) drive but that too failed. So I re-installed the OS X (10.6.3) on the new machine with the intention of trying to migrate user data from the old machine to the new install: this also failed – I was able to get to the login screen for the FileVaulted user, but the (correct) login password wouldn’t let me login. (This is the case whether you try using a Time Machine Back up to restore or using the Migration Assistant to restore from the external HD.) I expect the FileVaulted home directory was corrupted or perhaps even empty (accessed via Cmd-S on boot up and examining the volumes it showed 0kb in size).

Here is the solution.

1. Login as Administrator on the new machine
2. Use Bootcamp to create a new partition (as big as possible, especially if the FileVault home directory is a significant size)
3. Install (the same new version as on the machine) of Mac to the new partition.
4. Log back into the original install and open Disk Utility (in Applications -> Utilities). (When you re-boot press and hold down the Option key on start up which will give you the choice from which drive to boot the machine.)
5. Make sure you can see the external volume and that it is mounted. (You may need to run verify and repair.)
6. Select “Restore” and drag the external volume into “source” and the new partition into “destination”. Make sure you UNCHECK erase destination because you want the FileVaulted material on the new install of OS X.
7. The restore may take several hours. When it is completed, you should be able to re-boot from the new install and login to the FileVaulted account and access all data. If you have enough available disk space you can turn FileVault off and go from there. Even if not, when you are logged in to the FileVaulted directory you can simply copy the files you need to the other partition via Finder. Make sure you check they all copied properly and are accessible and useable before destroying the new partition.
8. When you have recovered everything you need, you can destroy the new partition. Log back into the main/original partition and use Bootcamp to recover the full disk space in the one partition. (There are a couple of tricks to this. Firstly, you need to make sure your current volume is the boot-up volume; go to System Preferences -> Startup Disk and make sure it is selected. Second, Bootcamp won’t let you erase a partition that it doesn’t recognise as a Windows partition, so you need to use Disk Utility to erase and reformat as MS-DOS before running the Bootcamp Assistant (select “Remove” and follow the prompts).