CSS, short for "Content Scrambling System," is an encryption system put into place on most commercial DVDs. It protects the DVDs' contents against pirating and provides regional coding – a feature that's used to include FBI warnings or commercials on the disc that you cannot skip. CSS encryption DVDs are the most common DVDs you will come across with movies.
What is CSS Encryption?
Put simply, CSS encryption is a simple line of defense against the world of pirating. Against certain DVD rippers, these measures are sufficient to prevent the unlawful copying of a DVD's contents. However, a growing number of software applications are cropping up that can easily bypass the encryption on a DVD and copy its contents.
The CSS standard is widely accepted simply because it gives manufacturers a reason to make their reading and playing devices compliant with the encryption measures. This is because CSS-encrypted media cannot play on noncompliant devices. Essentially, this forces the hand of every manufacturer to conform to a standard level of protective measures to ensure that they remain compliant and therefore usable by modern consumers.
CSS Stops Pirating
CSS encryption is intended to protect DVDs' contents from pirating. Depending on the type of DVD, these encryption measures are often sufficient to prevent many DVD ripping software applications from copying a DVD. Yet there is always a software application out there that can overcome the CSS encryption measures currently in place. In most cases, you can still copy any DVD regardless of its security. Only in certain cases, such as DVDs from Netflix or Disney movies, will most DVD copy software applications fail to decrypt the disc.
Most CSS decryption software is used to simply play DVD videos. However, a number of applications can copy a DVD to a hard drive and remove all protective elements from the contents. This means that the software completely bypasses a DVD's Macrovision, CSS encryption, region codes, and user operation prohibitions.
CSS Key Sets
Each DVD with CSS encryption has a set of keys hard coded internally for protection against data copying. While these keys do not prevent the raw image of a DVD from being copied to another media device, they do render any copies unusable. These keys can only be retrieved through proper authentication measures used by traditional DVD players.
Each CSS key set is licensed by the DVD Copy Control Association to be included in such things as DVD movie releases, drives and players. When the term "key set" is referred to generally, this includes the authentication key needed to secure a CSS handshake with the descrambler, the key for the disc itself, and the key for the player, among others.
The key set is stored on the lead-in portion of the CSS encryption disc, an area meant for reading only by compliant drives. This is specially designated because the data is to be read in a special way. The keys cannot be counterfeited, which prevents a simple copying of all of the disc's data.
Newer Encryption Methods
While the 40-bit key size of CSS encryption has provided some protection against pirating, it is still not quite enough. Newer DRM schemes have been put into place for greater protection. Some of these are Content Protection for Recordable Media (CPRM) and Advanced Encryption Standard (AES) through the Advanced Access Content System (AACS), a scheme used by HD DVDs and Blu-ray Discs. Both of these DRM schemes provide 56-bit and 128-bit key sizes, which make copying a DVD even more difficult for DVD copy software.
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