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My setup here is several MBPs backing up to an Apple Time Capsule. Backups are encrypted.

  1. I boot to recovery mode on the MBP I want to restore to (Cmd+R).
  2. Choose to restore from a Time Machine backup.
  3. Choose the Time Capsule in the list, and enter its network password. Works fine. I can now see the backups.
  4. Choose the particular MBP backup image I want to restore, and am prompted for its encryption password.
  5. Enter this, but it doesn't work. Wrong password, apparently. Tried repeatedly.

If I boot the MBP normally I can see in Keychain Access that the password I'm typing is 100% correct. No doubt about it.

I made sure to set the keyboard language correctly in recovery mode (it defaults to US English but I'm British). Still locked out.

I can browse the backup just fine when macOS is booted. I doubt the backup is corrupted but, like I say, in recovery mode I'm not even getting far enough to find out. The password for the encrypted backup image just isn't being accepted.

I've had this happen too in the past when I was utterly sure I had the right password, and I ended-up just abandoning the backup and starting with a fresh install. I can't do that here.

Anybody got a clue as to how I can access this backup? Why do I have a feeling I'm encountering one of those serious bugs that Apple knows about but brushes under the carpet?

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An update for people in 2019. We had the same problem, luckily we could still access the keychain and check. In our case the password was truncated to 28 characters from the 32 we had written.

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I think I figured this out and it's extraordinary. The issue appears to be that Apple's encryption for Time Machine backups only accepts 12 characters. Yet there's no error message, so you can enter longer passwords than this and it will simply truncate what you type and then record it in the Keychain.

So if you set the password 1234567890123 (13 characters) for an encryption password when initially creating the Time Machine backup, it will actually use 123456789012 (12 characters) and not inform you at any point. And because it's now stored in the Keychain, you will never have to type it again except in an emergency so will never know — until it's pretty much too late. When you need to restore the backup, you type the 13 character password and Time Machine will not accept it!

I think I'm correct here, but I might be wrong. I thought I'd share this just in case it's useful to anybody else.

So the solution:

  1. Ensure the keyboard is set to your nationality (UK or AUS English) by clicking the flag icon at the top right when in Recovery Mode.
  2. Type only the first 12 characters of your Time Machine encryption password. Prob best to write it out and count the characters, and then type it in.

Let me know if this solves your problem.

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