I formatted one partition on my external drive as MacOS Extended (Journaled, Encrypted).

Now when I open Time Machine and want to use that partition I see a checkbox Encrypt backups.

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Because I don't want to encrypt my backups twice I unticked this checkbox. But when I continue Time Machine asks me for the password of this partition to be able to turn off the encryption.

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I do not want to turn it off.

How can I use already encrypted disk?


This unbelievable problem has simple solution. Just leave the checkbox ticked and the encrypted partition will be used as is. No double encryption.

If you check the help ? there is written that the disk does not support encryption if the checkbox (Encrypt backups) is dimmed. Hence implying Time Machine is using disk encryption not another one on top of that.

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So the checkbox is just for people who had not prepared the disk yet.

  • For a little added explanation, when you check the box to encrypt your backup it doesn’t actually just encrypt the backup but the entire partition of your external Hard Drive. So even with an unprepared Hard Drive, if you choose to encrypt your Backups, everything else on the partition will be encrypted as well. – Kevin Grabher Jan 16 at 20:15
  • Exactly. I just did not understand that Apple thinks that showing users checked checkbox is indication of (already) used disk encryption. – A.D. Jan 17 at 15:27

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