How does CD copy protection work?

I don’t understand how companies can do anything to prevent people from copying CD’s and DVD’s. Wouldn’t it be a very simple matter to write a program that examined a disk then put a mark on the blank everywhere there was a remark on the original?
The only possible sollution that I can think of is if the got all of the creators of copying software to have their programs check if the author allows copies or not and then follow those wishes.

I can’t 't answer this question myself… just thought I’d point you towards a great resource. CD Freaks is pretty much the place to go for anything cd or dvd related.

CDs were designed before PC-based CD-copying became commonplace, so there are almost no measures in place to restrict copying. The initial assumption was that the average consumer simply wouldn’t be able to copy CDs, and for a long time, this was true.

Later, the PC-based recorder came along. Soon after, it became inexpensive, and blank CDs became very inexpensive. Copying of audio CDs soared.

The only exception to this is stand-alone CD recorders, which were intended to be easier to use and more convenient that PC-based recorders. The hope was that they would draw the copying customers away from PCs. These implement the Serial Copy Management System used by other digital audio recorders (such as digital audio tape recorders and minidisc recorders) and require special “music” CDs.

When the DVD was being designed, the movie studios (who were planning to release their properties on DVD) looked at the CD situation, gasped, and got the DVD Forum to include a much more complex system of measures to restrict DVD copying.

These included technical measures such as file encryption (to impede disc copying) and Macrovision video distortion (to impede copying of the analogue video signal from the DVD player to tape). There were changes to the PC-based consumer recorder design that prevented it from copying parts of the data used by the DVD player to decrypt the movie.

These technical measures are completely optional for people releasing video on DVD. These measures do not apply to data released on DVD.

There were also legal mesures that attempted to make all attempts to curcumvent the technological measures illegal. This is currently the subject of much controversy.

Another note: some audio discs that incorporate “copy protection” intended to make then difficult to copy on PCs are not allowed to carry the CD logo, because their contentsdo not conform the the audio-CD standards.

Here’s an older thread about CD copy protection.

The short answer is they can’t do anything to keep people from copying CDs and DVDs. If you can listen to a CD, watch a DVD, or play a computer game, then you already have access to all the data you need.

What they can do is take advantage of fleeting technical differences between their mastering equipment and your CD burner to make discs that you can’t burn an exact copy of, or between an audio CD player and a computer CD drive to make music discs that some CD-ROMs (very few, these days) won’t be able to read. I say “fleeting” because burners are getting more flexible over time, and hackers are learning to reproduce copy-protection features that were previously considered uncopyable.

But even uncopyable features aren’t a big problem: no one really needs exact copies, they just need working copies. For example, it’s impossible to make an exact copy of an encrypted DVD with a consumer-grade DVD burner, but you can easily decrypt it (just like your DVD player does when you want to watch the movie) and make a copy with no loss of quality. Some PC games check for physical features of the game disc that are difficult or impossible to copy, but it’s easier to just patch the game so it doesn’t check for them anymore.

Here’s a description of how one fairly common CD protection software works