You can move files to or from an encrypted disk image as easily as you can from a non-encrypted disk image. Follow these steps to create an encrypted disk image:
- Open Disk Utility (/Applications/Utilities/).
- Mac OS X 10.4, 10.5 or later: Click the New Image button, or choose New > Blank Disk Image from the Disk Utility File menu.
Mac OS X 10.3 through 10.3.9: Choose New from the Disk Utility Image menu.
- Enter a name in the Save As field. This name is used for the disk image (.dmg) file.
- Change the save destination if you wish to.
- Select a size for the image file from the Volume Size pop-up menu (Size in Mac OS X 10.3) .
- Choose a volume format if you don’t want to use the default Mac OS X Extended (Journaled).
- Choose an image format. You can use “sparse disk image” for a disk image that only uses as much space as it needs, rather than a set amount of space. If you’re not sure, use “read/write disk image” choice.
- Choose 128-bit AES (and/or 256-bit AES in Mac OS X 10.5 or later) from the Encryption pop-up menu to encrypt the image’s contents with a password. If you don’t choose an encryption, your new image won’t be encrypted.
- Click the Create button.
- Enter and verify a good password in the dialog window that appears. This password will be saved in your keychain by default, or you can deselect “Remember password (add to keychain)” if you don’t want that. You can store the password in the keychain both for convenience and for reducing risk of password loss.
- Click OK.
Important: If you forget the password, data stored in the encrypted disk image cannot be retrieved. If you have saved the password in the keychain file, the password will be available to you there.
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