What is a CSS and should I care?
"Intro to Content Scrambling System"

CSS ("Content Scrambling System") is an encryption system that most commercial DVDs use, and all DVD players need to understand. It's alleged purpose is to stop piracy, however it also enforces region coding, non-skippable FBI warnings or commercials and many other artificial restrictions.

Links to a cryptoanalysis of CSS can be found below, but CSS also consists of one other element: The CSS license. CSS is still being treated as a secret, even though it's dirty secrets have been available to the general public since November 1999. So in order to incorporate CSS into a player or other device, a company has to sign the CSS license, which is used as a further means to enforce the various restrictions put on customers through the CSS access control mechanism.

DeCSS

The software was released in the final days of october, 1999. It got considerable media attention during the first days of november, 1999.
DeCSS is a very simple windows tool that allows decryption of a CSS encrypted movie DVD and the copying of all or selected files from it to the harddisk.

It should be mentioned (again), that DVD rippers had been available for a long time already. For some reason, this fact did not get much media attention, which might be the reason many journalists saw DeCSS as the "first DVD piracy tool". The main difference between the "1st generation" rippers and tools like DeCSS and DoD Speed Ripper are that the older rippers do not decrypt the DVD at all. Instead, they let a DVD player do the decryption and hook themselves into the video or other suitable drivers, copying the data stream after decryption. The "2nd generation" software do actual decryption.

While this might be used for piracy in theory, it leaves you with a large volume of raw data in practice. A typical movie DVD contains 4 to 6 individual .vob files of 1 GB size each (the last file may be shorter) plus whatever special features might be on the DVD. The total data volume of a typical movie DVD is between 7 and 9 GB of data. You can't burn this to CD, since a CD only holds 650 MB of data - the 1 GB .vob files don't fit. If you keep it on your harddisk, then said harddisk will quickly fill up. An 18 GB drive can hold two DVD movies, but costs considerably more than original copies of those would cost. The same holds true for all other media that can store this amount of data, including writeable-DVDs.
At this point in time, the only people for whom DVD piracy is profitable are the professional pirates who own expensive equipment and couldn't care less for any encryption, since they do bitwise copies anyways, which means that their pirate copies are precise duplicates of the originals, including the CSS encryption. The DVD player will notice no difference between such a copy and the original version. CSS can not stop this kind of piracy.

Worse yet, this kind of piracy has been around since 1998 - long before DeCSS was ever written.

It is interesting that Jim Cardwell (Warner Home Video) completely agrees with most of the points made above. The only thing missing from his thoughts is the conclusion from his "There's no real economic incentive for anyone to hack this product" to the reason why it was done nevertheless.
More support for our arguments is coming from other industry players. The Israel-based company anti-piracy technology company TTR, for example, has published a whitepaper about CSS containing very much the same arguments.
Both the DVD CCA and the MPAA also can hardly claim ignorance to the fact that DVD piracy was a serious problem long before DeCSS. Why they still blaim DeCSS to "enable piracy" is beyond me.

Read the rest here