Once you have downloaded the image, double click the file to mount the virtual disk. Then, open Disk Utility located in Application>Utilities. You should see the virtual disk mounted in the left pane, directly under the image file. Make sure the USB flash drive is in write mode an insert the drive into a free port. The volume will mount, again showing the volume name directly under the device name, in the upper portion of the left pane. Select the ‘pgpboot’ volume that was mounted from the disk image and click the restore tab in the main window of the interface.
This will set the recovery disk volume as the source for restore. Now click and drag the volume of the USB drive to the destination field. Click the ‘Restore’ button in the lower right of the main window. (Warning): this process will erase all content of the USB flash drive. You will be prompted that the process will erase the contents of the USB drive and then prompted for an administrator’s password to proceed. Once the process is complete, eject the USB drive as you normally would and then lock the drive.
Power on the problem machine and hold option. This pauses the boot process and shows all bootable devices that are detected. At this point insert the Recovery USB flash drive into the machine. Make sure that the usb drive is locked at this point. A few moments after inserting the disc, the drive should show ‘EFI Boot’ with a USB drive icon as a bootable option. Click this icon to boot from the Recovery Drive. After a few moments you should see the BootGuard authentication screen. Authenticate with your passphrase for the encrypted drive in the computer. This will rebuild BootGuard on the encrypted disc. At this point a new screen will come up and state ‘To decrypt this drive, Press D’. DO NOT decrypt at this time. Instead, press the return key and which will then attempt to boot form the internal drive.
If at this time, if you still cannot boot the computer, we recommend you to slave the problem machine to another Apple computer and decrypt using a Symantec Encryption Desktop as the decryption process will be much faster or follow one of the other supported recovery methods below such as using Target Disk Mode. If you do not have another Apple computer available, you may decrypt from the Recovery USB drive, however please note this is a single threaded process and will take much longer to decrypt.