Making encrypted disk image takes hours?!

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Making encrypted disk image takes hours?!

Before I made a Time Machine backup, I wanted to use Disk Utility to create an encrypted disk image on an external hard drive. This way, my computer backup is password protected.

So I set the file for 200G at 128 bit encryption.

That was 12 hours ago. According to the progress bar, Disk Utility is still only one-quarter done with creating the disk image.

Is it normal for Disk Utility to take a full day (possibly two) to create a disk image of this size? Is there any way to create a password-protected disk image quicker? (And, for what it's worth, the external drive is formatted for Mac OS Extended, Journaled.)

Thanks for any advice on this...

MacBook5,1, Mac OS X (10.5.7)

Posted on Jul 30, 2009 11:29 AM

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Answer 1

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Pondini

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Jul 30, 2009 12:04 PM in response to RandyDrie

Hi, and welcome to the forums.

I'm not quite sure just what you're trying to do.

Are you planning to have Time Machine back-up to that encrypted disk image? If so, that's not going to work. When you start Time Machine, it will create a Backups.backupdb folder on whatever drive or partition you select, then place it's backups in that folder, not in a disk image.

If you want to encrypt your whole home folder, you can use File Vault (System Preferences > Security > File Vault). That will encrypt your entire home folder. But that's almost certainly vast overkill, and has many complications of it's own. Read up on it thoroughly before deciding to do it.

If you have a few files that you want to encrypt, create a (smaller) encrypted disk image on your internal HD, in your home folder. Then copy the documents into it, and securely-delete the originals.

Then TM can back-up your entire system "as is" -- without the overhead of encrypting OSX, your apps, configuration, and everything else in your home folder, but the disk image (and it's backup copy) will still be encrypted.

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Answer 2

Aug 9, 2009 11:41 AM in response to RandyDrie

You've probably resolved this already, but, in the interest of future people coming by here:

Yes, it's quite possible for a large encrypted volume to take this long to create. I don't know the details of the process, but there is a HUGE amount of DES/encryption computation required to make one of these things. Obviously, the larger the volume is and the slower your machine is, the longer it will take. The good news is that this effort is "one way" -- once the volume is created, data can move in and out of it very quickly -- you probably won't notice much of an impact.

An experiment: Create a 200 MB encrypted volume and time how long it takes to create this. It should take about 1000 times longer to create the 200GB volume you really want..

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