How to create a Encrypted Sparse Bundle Disk Image

Mac OS X 10.5 has a lot of built in features that a lot of novice users are not aware of.  One in particular is creating a encrypted sparse bundle.  Before I get to the creation of a sparse bundle, you might be asking yourself what is a encrypted sparse bundle.  On the Macintosh operating system a bundle or image is like a container, a representation of a virtual storage hard drive.  In the Macintosh Finder it appears as a file usually with the naming convention, “file.img” or if it’s a sparse bundle image one that grows in size as needed it will be named with a “.sparsebundle” at the end.  Once you double click on it it mounts what looks like a hard drive icon on your desktop.  A lot of times you may see this when installing a program such as firefox.  You download firefox and it has the name “firefox.img” you double click on the file and it mounts a hard drive on your desktop.  you open this virtual hard drive and you have the program inside.  This is only one example and you can download firefox if you want to see how this works.  But what if you want to create your own image or sparse bundle.  Apple makes it real easy to do this.  Here is how.  

Step 1: go to Macintosh HD/Applications/Utilities
Step 2: double click on “Disk Utility
Step 3: in Disk Utility go to File->Blank Disk Image…

Step 4: in “Save As” name your disk image
Step 5: you can also name your volume, this name will be used when the virtual disk is mounted.  Pick a Volume size and what format you want it to be.
**Step 5.5: If you are happy with the setting hit save and a disk image will be created.
But that last step will give you a image and not a Encrypted Sparse Bundle.  An encrypted Sparse Bundle is important to keep secure documents secured and to grow in size as needed.  If your laptop got stolen, no one would be able to get in to your image unless they had the password you set for the sparsebundle and it being encrypted gives it extra protection.  Let continue our steps…
Step 6: select “128-bit AES encryption or if you want to be extra secure, 256-bit AES encryption would work as well.
Step 7: also select what format you want.  Pick “sparse bundle disk Image”.  This will actually grow in size as needed. (you really only have to select this if you want it to grow.)

Step 7.5: Click Save
Step 8: you will be asked to provide a password.  Make sure when deciding on a password you pick a strong password, numbers, letters, symbols, etc… It will actually tell you if your password is strong enough.                    

Weak password Example
Weak password Example
Strong password Exampleknox-basics
Strong password Example

 Step 9: Now you can quit Disk Utility and you should see a virtual disk on your desktop. 
Every time you double click on the “.sparsebundle” or “.dmg” it will expand and ask you for your password. 


Here is another helpful hint.  Lets say you want to automate this.  There is a company that makes a product that does this.  The website is  They make a product called knox.  It gives you an interface to create encrypted sparse bundles and even organize them.  I highly recommend this product.  I use this daily.  I have included a short video of their product demo.  


October 3, 2008

I came across another really nice program called Espionage.  This program does the same thing but seems to be a little more seamless in it’s approach.  Instead of a menu bar icon it basically integrates in to the actual Mac OS.  It still uses the “Disk Image” technology but it hides it to the novice user and you never know you are using it.  You can go to to check it out.  Click on the link below to see a video of the product.

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