their products as trusted. "Hook IP" One particular trick that is often used is to include some patented technology, often as part of the trust establishment mechanism. This means that anyone wanting to implement the DRM in a way that will work with others is forced to license these patents. A condition of obtaining such a license is to follow the rules of the C&R regime itself. Thus a C&R body has a 20-year window to pursue legal measures against a "rogue" implementation on the grounds of patent violation, rather than having to rely on a DMCA-style regulation provided by the relevant government. The need to license hook IP patents also impacts anyone thinking of building a product covered by the GPL. One well-known example of a system employing such Hook IP is the DVB Common Scrambling Algorithm DVB-CSA, which though standardised by ETSI, includes patented elements that are only licensed to approved Conditional access systems vendors who agree to maintain the secrecy and integrity of the algorithm in their chip designs. Examples OMA DRM is governed by the CMLA C&R regime DTCP-IP is governed by the DTLA C&R regime References Intellectual property law Digital rights management