« TiVo expands to iPods, PSPs for TV playback | Main | Google Analytics Safari workaround »

Secure backup and storage using a disk image and an iPod

Posted in: Mac OS X, Non Stop Mac, Security, iPod

Disk UtilityIn case you lose your iPod (or any other external drive for that matter) or it gets stolen your data is in danger. I'm one of those people that constantly carries data on their iPod between two locations and I want to keep it safe. What follows is a brief tutorial aimed at those that want their data protected without investing in commercial software. In case you didn't know, you can increase your privacy pretty easily with features embedded directly into Mac OS X.

What I prefer to use for this task is the Disk Utility, you'll find it in - Applications > Utilities > Disk Utility. The easiest way to follow this tutorial is to do the work at the same time so I suggest you open it and just follow my instructions.

Once you start the Disk Utility the following window opens up:

Disk Utility main window

What we are interested here is creating a new image and in order to do that you'll have to use the - you guessed it - New Image option located in the upper left corner. Click on it once and you'll be prompted to give the image a name, choose the format and the encryption:

Image options

As the format goes, you can choose to create an image by using a preset between 2.5 MB and 4.7 GB (and 8 GB on Mac OS X 10.4) or you can use a custom size that fits your requirements.

Since the purpose of this article is to teach you how to make a secure backup of your files that you can modify on other Macs, I'm going to make a read/write image encrypted with 128-bit AES. Some will argue that this is not enough, and they're right. I wouldn't trust this for enterprise secrets but for information that most of us carry around this will be just fine. The purpose is not to give a stranger the easy way of browsing your files and not deter the NSA, there's commercial software that can give you enterprise-level security but that's beyond the scope of this article.

Once the image is created you'll be promted to enter a password, use something you can remember since without the password there's no way to access the image in the future:

Password screen

Once the password has been entered the image is mounted and ready for use on your desktop and will look something like this:

The created image

After you've filled the image with the data you want to carry around just eject it as you would any other image and connect your iPod to your Mac. Now for the easy part - copy the image to your iPod and you're done!

What I like about this approach is that it's fast, easy and it already comes with your Mac. This means that you can securely carry your data around and modify it on another Mac with no additional software.


Listed below are links to weblogs that reference Secure backup and storage using a disk image and an iPod:

» Life on a flash disk from solaris
I read an article once, somewhere on the net, about backing up important documents on a flash disk (iPod or any other removable storage). So if there is an emergency, such as a fire, flood or (heavens forbid) riot, you won't need to digg up your ... [Read More]


Very good tip!

Is there a good utility like this for Win XP?

Well you can download a free version of PGP (www.pgp.com) and use it for encrypting and decrypting. It is a pretty easy to use GUI program. Then you can just move the encryped file to your iPod and that will do the trick.

PGP would do the trick indeed.

The only thing is that I believe you need to have PGP installed on the machines where you want to open the encrypted file.

TrueCrypt (http://www.truecrypt.org) does the trick for WinXP and it's freeware.

abylon CryptDrive (a german product) at http://www.abylonsoft.com does the same, but it's commercial.

TrueCrypt also allows for a 'traveller mode' and hidden partitions for extra security.

For Win32, theres a util in DOS called CACLS, you can apply restrictions to differnt partitions with that. Usually applied only to cerian user accounts though, not sure how it would work between different machines. I've been locked out of drives that were formatted/used with different machines because it wasnt the exact same user w/ the exact same os install... pretty powerful. Will it work on an ipod? iono.

A very good tip and one I use for storing stuff that I want to protect on my local HD - rather than using FileVault. Be careful with this technique on an external drive however. If you unplug or power down the external drive without unmounting the disk image - the image may become unusable.

I also have to recommend TrueCrypt. Available from Truecrypt.org, it's free open source software.

Quite simply the easiest and most secure way to store your data.

Good article. If you don't want to do this all by hand, look for the excellent, free tool iPod Backup:


I don't have any connections with the developer, just a very satisfied user.



When I click on New Image I get a different dialog box. All the options are naing and save as then after clicking save it pops up and says "resource unavailable"

Carly, you need to unselect any drives before clicking on New Image. This way there will be no "resource unavailable" message and everything will work just fine.

okay I am a novice with mac. I understand till we get to eject the disk image ??? Sorry for my ignorance but what does that mean?


john > every disk image has to be mounted. When you get one and double click on it, it mounts and therefore another icon appears on the desktop, similar to the last one in the article. Now you're able to browse the image like it were a standard folder.

When you're finished working just take the "mounted" icon of your image and drag it to the Trash. The Trash will appear as one big Eject button and the image will be ejected. If you followed the tutorial, no one without a password will be able to mount and browse the image.

Ahhh - okay, thanks for the help!

Don't forget, you can also create SPARSE images, which are "growable", meaning if youI make a 5 GB SPARSE image, but you put one 2 MB file in it, the whole image is only 2 MB but can expand to 5 GB.

Another option for added security is to place images within images, all encrypted with different passwords.

You can do this through Disk Utility or using the hdiutil command from the Terminal. More info here...


I use the BestCrypt program and really like it. It make mountable drives on your system. The drives are actually encrypted files stored on your hard disk. All you have to do is move the encrypted file to your iPod to do a backup. You have to pay a little for it, but when it comes to my data...I want somebody standing being the product. It really isn't that expensive and it helps them keep improving the product.