What does De-Content Scrambling System (DeCSS) mean?
De-content scrambling system (DeCSS) is software that can decrypt the content of commercially released DVD video disks that are protected through a content scrambling system (CSS) encryption technique. DeCSS can be used to make pristine unauthorized copies of video DVDs.
CSS technology is outdated, relying on only a 40-bit encryption method that can now be broken by a modern desktop computer in a matter of seconds. DeCSS is still used and the code is built in to various redesigned implementations and widely available on the Internet.
Techopedia explains De-Content Scrambling System (DeCSS)
A Norwegian teen, along with two anonymous authors, first released DeCSS in late 1999 through an electronic mailing list. DVD rippers already existed, but the DeCSS system worked differently by reverse-engineering a software DVD player.
DeCSS was developed and released without a license from the DVD Copy Control Association, which developed CCS and is responsible for DVD copyright protection. DeCSS contains the CSS algorithm and made this algorithm public domain. The author of DeCSS was prosecuted (unsuccessfully) in Norway.
DeCSS is illegal to use or download in many countries but is nevertheless widely available on the Internet.