Errors when trying to open up a disk image that has been comp. & encrypted.

Question

I have an old 15” PowerBook G4 that I purchased back in 2004 that I wanted to backup the data on in preparation to sell it. The PowerBook has Leopard (Mac OS 10.5) installed on it. I used my Leopard installation DVD to boot the computer up and then launched disk utility (v. 11.0 (252)). I wanted to make a disk image (.dmg) of my entire “Macintosh HD” partition, so after unmounting the partition (otherwise you get a “resource busy” error message), I selected File -> New -> “Disk Image From...(<hard drive partition>)”. The next screen presented me with a name to type in for the saved disk image file and options to compress and encrypt (128 or 256 bit AES) the image. I could not get the image to begin creation when I had both compression and encryption set. I kept getting the error message “Unable to create (error -60007)”. So, I opted to create the disk image with just compression selected. This worked fine and I was able to select the image (let’s call it disk_image1) and perform an Image -> “Scan Image for Restore...” successfully as well as mount the image and open up files (the verification process took a long time before the image mounted, but it was successful).
Next, I moved the Firewire 800 external HD containing “disk_image1” to my new MacBook Pro (Snow Leopard installed) and opened up disk utility (v. 11.5.1 (298.1)). I was able to successfully mount the image and browse and open up files with this updated version of disk utility. I then attempted to convert the disk image I just created to a new disk image (let’s call it disk_image2) via Images -> “Convert...”. I selected “disk_image1” and then named the new image (disk_image2). I then selected compression and 128bit AES encryption, entered in a passphrase and started the process. Everything worked great in creating “disk_image2”, but when I tried to open up the image either in Finder or within disk utility, I got error messages. In disk utility, I got the message “Unable to attach “disk_image2.” (Authentication error).” and within Finder, I got “The following disk image couldn’t be opened” disk_image 2 (Authentication error). Note, I was never asked to provide the password I used to encrypt the image nor did I ever select to save it in my keychain. Just as a precautionary measure, I check my keychain and did not see the password for the encrypted image saved in there.
Is there a bug within disk utility with the way a compressed & encrypted image is created or a problem with the authentication process for an encrypted image?

Answer 1

I have not had this happen to me, but have read similar stories from people on these boards for years. I think saving an entire OS X boot disk to a disk image is asking for trouble. If anything goes wrong, one byte of data is copied incorrectly. it can render the entire image unmountable and all of the data in it inaccessible.
I'd use Disk Utility's Restore button (or a program like SuperDuper or Carbon Copy Cloner) to make a complete copy of the hard drive onto its own hard drive, skipping the disk image. If any bit of data gets dropped then only one file is affected, instead of the whole works. Do you have any other stuff on that external drive? If not, just erase it and try again, copying everything directly to the drive instead of to a disk image.