OS X Encrypted Disk Image
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What is an Encrypted Disk Image?
An encrypted disk image (.DMG) is a 128-bit or 256-bit encrypted file that, when opened, will prompt the user for a password. Once authenticated, the disk image will mount on the desktop allowing the user to copy data to or from the mounted disk image before unmounting the image to secure it.
Creating an Encrypted Disk Image
- Launch the Disk Utility application. Go to Applications > Utilities > Disk Utility.
- Go to File, then select New Blank Image. Enter a name for your image.
- Select the size (this is permanent, and cannot be changed).
- Under "Encryption", select "AES-128 Encryption" (or 256-bit in Leopard, 10.5).
- Click OK and enter your password twice. Be sure to uncheck "Remember password in Keychain".
- Your DMG will mount on your desktop, ready for files. To close it, control-click the icon and select "Eject".
