November 2002|The FCC has mandated that the digital television transition be completed by 2006. Although consumers and engineers are excited about the improved picture clarity, higher resolution, and other technological wonders offered by HDTV, studios and content creators are distressed about the gaping security hole in first-generation high-definition (HD) devices. These early devices use insecure analog component video connections that pirates can easily exploit.
The need for component video arose because traditional S-video and composite video connections couldn't handle the increased HDTV resolution nor could they provide acceptable picture quality. By contrast, component video cables can support all existing HDTV resolutions (720p, 1080i, etc.) and eliminate most of the noise introduced by analog S-video and composite connections. Furthermore, as a result of higher cable qualities and improved digital filtering in displays, component video connections are capable of stunning picture quality that is virtually indistinguishable from pure digital connections.
Unfortunately, this improved picture quality attracts not only consumers, but also pirates. Pirates are interested because they can capture the video output intended for an HD display and create a high-resolution master. While copies made from component video connections are not exact digital duplicates, it is very difficult to distinguish them from the original. Consequently, major studios have been reluctant to release movies in HD format and this has in turn limited HDTV to a niche market of a few million early adopters.
Digital Isn't Necessarily Better
Given the content producers' concerns about analog component video connections, several industry groups have proposed replacement digital interfaces. The leading digital alternative is the Digital Visual Interface (DVI). DVI is a special-purpose, high-speed interface that is intended to transport uncompressed digital video content to a display. DVI's capacity and speed (up to 5Gbps) let you transmit uncompressed HD streams. By contrast, other digital interfaces require HD content to be compressed, and the compression process slightly degrades picture quality (although the impact may not be visible to the typical consumer).
Although originally intended as a high-speed interface for connecting computers to Liquid Crystal (LCD), plasma, and other digital displays, DVI has been adapted for use in the consumer market (i.e., set-top boxes, DVD players, and the like). Initially, DVI appears to be an ideal match for the HD devices. It can transport 720p and 1080i streams and offers unparalleled picture quality. Unfortunately, a careful examination of the specification reveals that DVI is just as vulnerable to hackers as analog component video connections. Furthermore, since DVI transports uncompressed digital content, pirates can use it to create pristine digital copies of the original HD stream, which should petrify any content owner.
Fortunately, unlike an analog connection, you can secure DVI via the High-bandwidth Digital Content Protection (HDCP) protocol. The goal of HDCP is to transport secured content from a source device (i.e., set-top box, DVD player, etc.) to a display device. Since it is a display-centric protocol, it does not permit recording to digital VCRs or other recording devices.
The HDCP process consists of three phases: authentication, encryption, and renewal. Authentication is the process by which the source device (i.e., DVD player or HD set-top box) and display device authenticate (verify the legitimacy of) each other. Once each party knows the other side can be trusted, the source device encrypts (scrambles) the content and transports it to the display. The display then decrypts and displays the content.
The final HDCP phase is renewal. While the HD stream is playing, the display device re-authenticates the source device every two to three seconds by exchanging encrypted information about the current video frame. Should either party fail during re-authentication, the HDCP session is abandoned and the stream immediately ceases playing.
If a large number of boxes from a specific manufacturer is compromised, the Digital Content Protection LLC (the body responsible for issuing copy protection keys) sends System Renewability Messages (SRMs) to source devices. These SRMs contain a list of devices that are no longer authorized to play HDCP-encrypted content. After a source device (i.e., DVD player or set-top box) has processed the SRM blacklist, all compromised devices are prevented from playing encrypted content.