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I am thinking about upgrading to Mac OS X 10.7 Lion, because it offers full disk encryption.

However, if I use Time Machine with on an external hard drive, will the Time Machine backups be encrypted as well? If not it seems to defeat the purpose of whole system encryption. :p

Also, if the Time Machine backups can be encrypted, how does it handle restoring from a Time Machine backup onto a new system?

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up vote 3 down vote accepted

It took me a little while to find the "Encrypt backup disk" checkbox, so I thought an answer explaining that may save you some time.

Press the "Select Disk…" button in the Time Machine System Preferences panel, and the "Encrypt backup disk" checkbox is enabled when you select a disk. enter image description here

I decided not to encrypt my Drobo after reading Alrescha's important note about not being able to use an encrypted disk with older versions of OS X than Lion.

But I was curious to see if Apple would warn me: enter image description here

(See also "If I encrypt a Time Machine backup disk, is the entire disk encrypted or just the Backups.backupdb directory?".)

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Just awesome commentary and picture. You can edit the chosen answer to make it better. Most people welcome the change and they get notified as well as the ability to revert / edit your changes if for some reason they don't agree. Thanks for putting this out - seeing the UI really makes the answer STICK :-) –  bmike Aug 9 '11 at 15:08
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You should not encrypt your Drobo. Drobo does not support whole disk encryption and specifically warns against using it: support.drobo.com/app/answers/detail/a_id/132/~/… –  zzz Aug 9 '11 at 16:44
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Time Machine does have a checkbox to encrypt the backup, but it will read, encrypt, and write every block of the disk - which can take a long time. If you are using a new drive it is much faster to encrypt it with Disk Utility first.

The encryption is handled by the OS – not Time Machine. Lion will prompt for the password whenever the disk is attached. Once the password has been entered it looks like any other disk to Time Machine.

n.b. you will not be able to use an encrypted disk with older versions of OS X.

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+1 for "you will not be able to use an encrypted disk with older versions of OS X" –  Thilo Aug 8 '11 at 4:02
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Time Machine backups can be encrypted as well. When setting up Time Machine, it'll ask if you want to use encryption and to enter a password.

I've not tried to restore to a new system, but I would think it would just ask for the password and work fine after you enter it.

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Note that you can only encrypt Time Machine backups on a directly attached drive (internal, Firewire, USB or Thunderbolt), not a network drive or a Time Capsule. –  Mike Scott Aug 7 '11 at 14:56
    
This is incorrect, you can create encrypted back ups using a Time Capsule. You need to create an encrypted sparsebundle file. michaelnozbe.com/mac-osx-lion-secure-backup-to-time-capsule-wi –  skub Aug 8 '11 at 1:13
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