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I have found countless blogs and tutorials how to encrypt an external drive using Mac's extended journaled encrypted format, but I couldn't find anybody stating the standard behind it. I know that FireVault 2 uses XTS-AES 128 encryption, but is that the same used for the external format or are the hard/flash drives simply assigned with a mounting password? Any link for clarification or simply a statement would be very appreciated.

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Cannot speak with authority, but FileVault2 is built on top of that new hard disk encryption feature, so this is also almost certainly the same algorithm (at least by default, maybe there are other options). – Thilo Apr 18 '12 at 9:45
  1. Open Terminal (located in /Applications/Utilities/ and type:

    disktutil cs list
  2. Then look for the entry of your standard drive, e.g.

    Name:                    Macintosh HD
  3. Look further down to find out the encryption type:

    Encryption Type:         AES-XTS

The latter is what I see when using this command in OS X 10.8.2, so you can assume that AES-XTS stands for the AES-XTS 128-bit encryption used in Mountain Lion.

I expect Lion to use the same encryption model, but I can't verify it because I have no Mac that's running Lion. However, the diskutil command should help you to find the definite answer.

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