Getting Your Digital Sh*# Together – Part 2
published by Holger Bartel on
Security becomes more and more important everyday. Here's a tip on how to better secure your sensitive files. First things first: If you don't have a login password set for your computer, you should set one now. Don't ask or complain, just do it.
Securing Your Your Sensitive Files
Like everyone, you probably have sensitive files on your computer that you want to keep them safe. Even though you do have a password set to login to your computer, you might want some extra security, especially if you keep these files on an external drive to save some hard disk space on your machine.
An easy way to do this is to create an encrypted disk image. The best way to go about this is to use the so-called "Sparse Bundle Disk Image" files. You can recognise these files by their extension ".sparsebundle".
When creating a sparse image, you choose a size, preferably somewhat matching your current needs. Let's say you have 5G of data and know that there will be more coming, create an image with 10G, just in case. After putting the first 5G into the disk image, you still have 5G of space available, but the file itself will only take up 5G of space at that time. A Sparse Bundle Disk Image automatically increases in size as you go along.
To create a Sparse Bundle Disk Image, open Disk Utility found in /Applications/Utilities/Disk Utility.app
Click on "New Image", name the file and give the image a name as well. Select or input your desired size and choose the Encryption type from the pulldown. From the Image Format at the bottom of the list, select the Sparse Bundle Disk Image. All other choices can be left at their defaults. After clicking "Create" you will be asked to set a password. Do not forget this password, otherwise your files in the disk image cannot be recovered.
There you go, you have just created your first Sparse Bundle Disk Image.
The resulting file will behave similar to an external disk or a DVD. To open this image, just double click the file and it will mount the disk image for you, to unmount (and basically close the file to prevent people read from it) you'll have to eject it.
Another nice thing about these files is that you can adjust their size later on, when you have used up the – in this example – 10G. This can easily be done via Terminal. You'll have to unmount the image before you can modify the file.
Modifying Your Existing Sparse Bundle Disk Image
In this example the path to the file is in your home folders Documents folder, but you can basically keep them anywhere you like, even on an external hard drive. If you don't know how to type the path, you can also enter the command first and then drag the image file into the Terminal window, which will output its path.
To increase the image size, e.g. from 10G to 25G, type:
hdiutil resize -size 25g ~/Documents/filename.sparsebundle
For a list of options and help with the hdiutil command, you can type:
Enjoy More Safety
Your digital life just got a little safer again and I hope you'll feel better knowing that you're sensitive files are in a more secure place. Remember that the disk image needs to be unmounted to be "closed" and if you are not the only one using your computer, saving the password in keychain will pretty much render it useless, since you will not be asked for the password when opening.