Encrypting a Time Machine backup on an encrypted disk?

[steve62388]

A question for you.

I have an external disk and it is one single partition and encrypted using FileVault. I use this disk for data and I'm also going to use it to backup with Time Machine. If I choose to encrypt my Time Machine backup how does macOS handle that? Does it double encrypt or is it smart enough not to bother with the TM encryption?

 

[Weaselboy]

Does it double encrypt or is it smart enough not to bother with the TM encryption?

The latter. It will see that the drive is already encrypted and just keep on using it for backups.

 

[KALLT]

Time Machine itself does not encrypt anything, it relies on the disk encryption of the target disk. The checkbox in the Time Machine setup merely assures that the target disk is encrypted or that the system will be instructed to encrypt the disk first. All you need is a disk that is formatted as ‘Mac OS Extended (Journaled, Encrypted)’.