How do I change Time Machine's encrypted backup password?

Hey JSheward,

I tried doing the same thing and got the same results. Turns out that the only way to change the passphrase on a disk image is to convert it, since the "Change Password" option is reserved for volume (drive) encryption only. Unfortunately my Time Machine backups aren't in a disk image so I don't know whether this will be successful or not.

1. Remove the drive from Time Machine.
2. If the drive is connected over the network, connect the drive directly to your Mac (via USB, Thunderbolt, etc.)
3. Open Disk Utility.
4. In the top menu bar, select Images, then click on Convert.
5. Select the sparse bundle image and click Choose.
6. A menu with some options should appear. Select the encryption type, and enter the new password when prompted.
7. Set the Image Format to "Read/Write".
8. Save the new disk image directly to the Time Machine drive, where the old image is located. For now, give it a different name than the original disk image. If prompted, enter the password you used for the original disk image.
9. Wait for the conversion to complete. This may take a while, given the large size of the .sparsebundle image.
10. When conversion is complete, give the new disk image the same name as the old one. Delete the old disk image (or back it up somewhere first).
11. If the drive was a network drive, reconnect it to the network the way it was before you connected it to your Mac.
12. Re-add the drive in Time Machine. Hopefully it should detect the new disk image and continue backups from there.

I want to change the password used to encrypt my Time Machine backup i.e. the .sparsebundle, without deleting the existing backup and creating a new one. I have seen previous advice regarding using DiskUtil to do this, however the "Change Password" function under File, is greyed out when trying to do this. I am running MacOS Mojave.

ref:

Change password to Time Machine backup https://discussions.apple.com/thread/8288275

Does the Time Capsule appear on your desktop (or in Finder) as a drive? If yes, proceed with the above steps if possible (but ignore steps 2 and 11). Be warned, though, that the process will likely take much longer since you'll have to write to the Time Capsule over the network instead of USB.

Also, in step 8, if you have sufficient space on your Mac (and you're don't have enough space on the Time Capsule), save the new disk image directly to your Mac with the same name as the original disk image. Once that's done, copy it over to the Time Capsule and remove the old disk image.

EDIT: Oops, replied to the wrong reply. Hopefully the admins will sort this out :)