Apple’s FileVault encrypts your whole home folder, which is overkill
for many users, needlessly slowing access to their files and increasing
the risk of data corruption.
DropDMG lets you use the same encryption technology to protect a select
group of files from prying eyes. Each group of files is stored on an
encrypted disk image. Each disk image can hold as many or as few files
as you want and can have its own passphrase. The files will be secure if
your hard drive is stolen or if you send the disk image across a
network.
To create an encrypted disk image with your files:
- Open DropDMG’s preferences window and select one of the .dmg
formats. Choose “read-write” if you want to be able to modify the
encrypted files, or choose one of the compressed formats to save
disk space.
- Check the box next to Encrypt using passphrase and enter a
passphrase. Check the Delete original after Creating box if you
want DropDMG to delete the original files when it’s done, leaving
only the encrypted version.
- Drag the folder containing your files onto DropDMG’s status window,
or choose New from Folder/File… from the File menu and
select the folder. DropDMG will then create an encrypted .dmg
file with the contents of the folder.
To access the encrypted files:
- Double-click the .dmg file. The Finder will ask for your
passphrase, and then mount the image as a white volume icon on your
desktop. Inside it will be your files, and you can access them as
normal.
- When you're done using the files, eject the volume. The files will
now be inaccessible without the passphrase.
Here are some additional tips:
- You can encrypt files with just one step by saving DropDMG’s
preferences as a Configuration. From DropDMG’s Preferences
window, choose Save Configuration As… from the Configuration
pop-up menu and then enter a name for the configuration. When you
want to encrypt a folder, make sure that the configuration is
selected, and then drag the folder onto DropDMG. It will use the
options and passphrase that you saved.
- Save time by using a Login Item to make some encrypted files
available whenever you log into your Mac. Choose System
Preferences… from the Apple menu. Click on Accounts, and then
select your account. Then click Login Items. Drag your .dmg
file into the list. Now, whenever you log into your Mac, it will ask
for the passphrase and then mount the image.
- The encrypted files don’t have to appear on your desktop. You can
use the Mount Image At… command to make them available inside
another folder.