Create multiple nested secure disk images

Jan 14, '05 11:12:00AM

Contributed by: Anonymous

If you don't think AES-128 is good enough to keep your secrets safe in an encrypted disk image, you can try using nested encrypted disk images. This simply means storing one encrypted disk image inside another encrypted disk image, with each disk image having a different password. You can nest disk images to as many levels as you wish. Doing this should result in the sensitive data being encrypted multiple times with multiple passwords before being written to the hard disk.

The following steps show how to nest one disk image inside another:

  1. Using Disk Utility, create a sparse encrypted disk image named "Outside".
  2. Using Disk Utility create a second sparse encrypted disk image named "Inside". Use a different password for each disk image. It is best not to remember the passwords in the Keychain when creating these disk images.
  3. At this point you should have files Outside.sparseimage and Inside.sparseimage on the Desktop, as well as an Outside disk icon and an Inside disk icon. Drag the Inside disk icon to the Trash.
  4. Drag the Inside.sparseimage file into the Outside disk icon.
  5. Drag the Inside.spargeimage file in the Desktop to the Trash.
  6. At this point you should have file Outside.sparseimage in the Desktop and file Inside.sparseimage in the Outside disk.
  7. Double click the Inside.spargeimage file in the Outside disk. This will make the Inside disk icon appear on the Desktop.
  8. Copy your sensitive files to the Inside disk. When you do this the data will be encrypted first with the password for Inside disk, then again with the password for Outisde disk before it is finally written to the Outside.sparsedisk file.
  9. When done, drag the Inside disk icon to the Trash, then drag the Outside disk icon to the Trash.
  10. To access the sensitive files, double click the Outside.sparseimage file to mount the Outside disk, then double click the Inside.sparseimage file in the Outside disk to mount the Inside disk
[robg adds: I haven't tested this one. Make sure you use different passwords for each, or it's no more secure than just one image...]

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