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.
Open Terminal (located in
/Applications/Utilities/Terminal.app) and type:
disktutil cs list
Then look for the entry of your standard drive, e.g.
Name: Macintosh HD
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.