[X4U] Copy of DVD with write protect

[Stroller]

On 9 Aug 2007, at 20:18, Michael Winter wrote:
> On Aug 9, 2007, at 1:47 PM, wilkinw wrote:
>
>> MacTheRipper for decoding!
>
> I may be wrong, but I thought MTR was only for video DVD's. Is the  
> disk in question a standard video DVD with the same copy protection  
> measures, or a data DVD?

As I wrote previously on 4 Aug 2007, at 21:44:

    I believe that if you "rip" with a program that simply removes  
the CSS
    "region protection" then the original DVD structure can simply be
    copied onto a blank DVD-R which is viewable using a household  
player.

    CSS stands, I think, for "content scrambling system" and it's the
    reason you can't simply drag & drop files from a store-bought DVD  
onto
    a blank DVD-R. The scrambled content requires a decryption key which
    is written in an area of the disk inaccessible to home DVD writers.

It is reasonable conjecture that the GPS's data DVD is encrypted with  
a key stored in this inaccessible area and that MTR will decrypt it.  
Of course, even if that guess is right, it doesn't mean that the GPS  
will play the decrypted DVD-R, but it's worth a try.

You can do a bitwise copy of any DVD on any o/s, so it's irrelevant  
that the friend's machine is a PC & yours a Mac. The same part of the  
DVD is unwritable by any consumer DVD writer, so in the event that a  
disk is copy-protected it's this that you've got to worry about. This  
special area of the disk can be stamped when DVDs are mass-produced  
in a factory, of course, but for one-off use the only way you can  
write to the "magic" area is by using an "authoring DVD-writer" and  
special DVD±R disks. I think I read that these are several grand to  
buy, but that vendors are only licensed to sell one to you if your  
name ends in "Studios".

I believe the magic area can be _read_ by any consumer DVD player or  
computer DVD drive - this is how the encryption code is read & used  
to decrypt the movie - but one might also conjecture that software  
DVDs (like this GPS map DVD) might utilise it differently. One could,  
for instance, leave the entire contents of the data DVD unencrypted  
but have one's software read the magic area - as long as it contains  
the string "12345" then you can be sure that it's not a homemade DVD- 
R backup. No decryption takes place here, the mere presence of  
*anything* in the magic area testifies that the disk is not a copy.

I guess that the game disks for Playstations, Xboxen and the Wii use  
the "magic area" in a similar way to prevent copying. I don't think  
there is any ongoing decryption as the game is being played but  
rather it is checked when the game starts. Aside from these, and from  
regular region-locked movies, I have myself only encountered one  
other special DVD which appears to utilise the magic area of the DVD;  
that was a Panasonic "Service Disk" which allows one to access a menu  
and enter codes to remove the region and macrovision from the "Q"  
Gamecube and from other of Panasonic's DVD players. I have not heard  
of any success copying this disk.

I hope this is clear. I realise after writing all that that I haven't  
defined encryption & decryption, so the distinctions made in my last  
couple of paragraphs might not be apparent. Please let me know if  
you'd like me to try again. :/

I'm sorry this doesn't directly answer your question, but I think  
it's impossible to know for sure if this disk is copyable or not. It  
costs you little to try MacTheRipper. If one knew the brandname of  
the GPS unit one might be able to research further, but I suspect  
that hacking the unit will NOT be trivial. I concur with Mr Winter  
that you should look into the manufacturer's media replacement policy  
- preferably before you need to use it. It might be possible to  
register the disk and purchase a replacement next month for your  
"lost" one, other companies require the scratched or damaged disk  
back before they'll issue a disk under such schemes; in this case you  
should check your insurer's policy on such software.

Stroller.