Why can't DVD's be copied without ripping?

[fxer]

I was curious, I've never known the actual mechanism which prevented you from making images of DVDs and burning them back to disc, and playing them as normal.

Is making a 1:1 copy of an (encrypted) DVD impossible? Is there some sort of key on the stamped DVD that won't be copied by a burner or what? Wikipedia could use help with the why also, simply stating: "Without descrambling first, any digital copy of the disc will be ruined and unplayable everywhere, including computers."

Someone asked me this question, and I couldn't answer it clearly, figured some techies here would know :)

[Trahald]

heres what i understand...

Is making a 1:1 copy of an (encrypted) DVD impossible?you can definately copy an encrypted dvd. a normal encrypted dvd has nothing that keeps you from getting the data off the disk. (we'll leave structure protection (ripguard, etc) that actually put physical errors on the disc in areas that wont need to be accessed during playback ) you can use windows explorer to pull the data off and burn it with your favorite application . but...
Is there some sort of key on the stamped DVD that won't be copied by a burner or what?yep.. thats the problem. the key can be read (because its needed for playback) and therefore used to decrypt the dvd. but keys cannot be written by consumer burning applications. the key is written to the original dvd as part of the replication process studios use.
Wikipedia could use help with the why also, simply stating: "Without descrambling first, any digital copy of the disc will be ruined and unplayable everywhere, including computers."they are right. because the key your dvd player needs wont be available, your resulting disk may work somewhat but the display will be a green blob at best and completely fail at worst.

[fxer]

That is pretty much what I guessed, however it raises the question ; how, and where on disc, is the key installed at the factory? Obviously it is installed in location that a DVD burner can reach (as the key must be read to play a disc properly), but not a place the burner can write? You can create your own CSS encrypted DVDs with Scenarist or something can't you? So then would your burner write the key to that DVDR disc for you? Is there an agreement on behalf of the DVD burner/media manufacturers to disable that ability?

[blutach]

Generally in the packs of the VOBs

Regards

[Trahald]

the title key is stored in the sector header( this is also where error correction data is ). each VTS on the disc has a separate key. a sector header is written with every sector of data just like cds.

the disk key is hidden in the control area of the disc (in the lead-in).

no commercial software allows you to add css. (its not in the spec dvd-r/etc spec)

[linx05]

no commercial software allows you to add css. (its not in the spec dvd-r/etc spec)
Adobe Encore does.

[blutach]

I'd just like to know why anyone would want to add encryption (particularly weak encryption like CSS) to their DVDs.

Regards

[setarip_old]

@linx05

Hi!Originally Posted by Trahald
no commercial software allows you to add css. (its not in the spec dvd-r/etc spec)
Originally Posted by linx05
Adobe Encore does.1) If, as Trahald mentioned earlier, the CSS keys are in the lead-in section of a DVD - and that section can ONLY be written to by commercial pressing - it would seem that those of us using non-commercial burners woudn't be able to avail ourselves to this capability.

The following is from a review of Adobe Encore at the newegg.com website:The CSS and Macrovision can NOT be output to DVD-R,+R,RW or DL disks due to physical limitations of recordable disks. This is not made clear for non-professional users.

[Brother John]

This is the the situation, if I remember correctly. Sorry, don't have any sources at hand.

On a DVD-R the physical location where the disc key would be stored is pre-burned (for lack of a better word) and thus cannot be used by any burner. On a DVD+R such a physically reserved area is not even defined.

The only way to produce CSS encrypted discs indeed is to press them. And of course you have to obtain a CSS licence first.

[Mug Funky]

Adobe Encore does.

really?

plenty of authoring programs allow you to compile formatted for CSS (in the image file, sectors of 2054 instead of 2048 bytes), but the actual keys and scrambling happens in mastering, not premastering (ie. at the replication plant).

CSS can't be burnt onto discs.

[linx05]

I've never tried to burn a DVD with CSS enabled. I just gathered it could after seeing this picture (http://www.imageupload.com/uploads/2c50c_css.jpg).

[laura_lee]

I lean a lot from this case.

[alstar1]

Is there some sort of decryping on a Windows XP disc so a person can get the key from it or is this a different Decrypt.

[Blue_MiSfit]

xp product keys are not tied to physical media.

[dwrigh62]

Have used some file recovery software{any reader]to try to pull from protected dvd and the result was green screen with sound.
Interesting thread

[Trahald]

regaurding css keys i meant actually writting it to disk (which is really the topic). not making hte dlt or an image. scenarist also supports css.

@setarip_old
thank you :)

[scanner]

Wasn't it in the early days, Css could be foiled just by taking a black sharpie and running it along the the lead in of the disc? I seem to remember it was, ??? John Johansen (name) that discovered this and he was immeditly sued for releasing the information.

[setarip_old]

@scanner

Hi!

I think you're confusing DVD CSS copy protection with SONY's 2 million dollar waste of money audio CD "copy protection" of two or three years ago...

[linx05]

@scanner
I remember hearing about that back when I was at school before I knew anything about DVD decrypting. I couldn't put my head around how that possibly worked. Times have changed.

[akupenguin]

@scanner
You're thinking of a different obfuscation scheme that was used for a few music CDs, to try to prevent playback on a computer. They would put a small track on the outside of the CD, containing a malformed filesystem. The computer would try to mount that filesystem, fail, and reject the CD entirely. By covering up those sectors with a sharpie, the computer wouldn't see the extra track, and would then happily play the audio part.
No encryption involved, and it the scheme didn't prevent playback on every computer even without the sharpie workaround.

[scanner]

Ok I knew it was something to that effect. Thanks for the further explanation it never did make any sense to me, but then anything sony tries does.:thanks: :goodpost: