DTCP is a copy-control scheme for digital video devised by five companies (called the "5C consortium"). HDCP is a similar copy-control scheme devices by only four companies (the "4C consortium"). Both of these schemes restrict what a consumer can do with digital video; both require a license if a device manufacturer is going to be able to implement them; both constrain the functionality of products in which they are incorporated. Both cost money to implement—the licenses are not free. DTCP encrypts video transmitted over a digital bus called IEEE 1394 (or "FireWire"). HDCP encrypts video transmitted over a different—and video-specific—bus called Digital Visual Interface ("DVI"). The encryption, in both cases, is meant to "protect" the content against the consumer, and to restrict playback of the content to "authorized", licensed devices.