High-bandwidth Digital Content Protection
High-bandwidth Digital Content Protection (HDCP) is a form of digital copy protection developed by Intel Corporation[1] to prevent copying of digital audio and video content as it travels across connections. Types of connections include DisplayPort (DP), Digital Visual Interface (DVI), and High-Definition Multimedia Interface (HDMI), as well as less popular or now deprecated protocols like Gigabit Video Interface (GVIF) and Unified Display Interface (UDI).
The system is meant to stop HDCP-encrypted content from being played on unauthorized devices or devices which have been modified to copy HDCP content.[2][3] Before sending data, a transmitting device checks that the receiver is authorized to receive it. If so, the transmitter encrypts the data to prevent eavesdropping as it flows to the receiver.[4]
In order to make a device that plays HDCP-enabled content, the manufacturer must obtain a license for the patent from Intel subsidiary Digital Content Protection LLC, pay an annual fee, and submit to various conditions.[5][6][7] For example, the device cannot be designed to copy; it must "frustrate attempts to defeat the content protection requirements";[7] it must not transmit high definition protected video to non-HDCP receivers; and DVD-Audio works can be played only at CD-audio quality[7] by non-HDCP digital audio outputs (analog audio outputs have no quality limits). If the device has a feature like Intel Management Engine disabled, HDCP will not work.
Cryptanalysis researchers demonstrated flaws in HDCP as early as 2001. In September 2010, an HDCP master key that allows for the generation of valid device keys was released to the public, rendering the key revocation feature of HDCP useless.[8][9] Intel has confirmed that the crack is real,[10] and believes the master key was reverse engineered rather than leaked.[11] In practical terms, the impact of the crack has been described as "the digital equivalent of pointing a video camera at the TV", and of limited importance for consumers because the encryption of high-definition discs has been attacked directly, with the loss of interactive features like menus.[12] Intel threatened to sue anyone producing an unlicensed device.[11]
Problems[edit]
HDCP can cause problems for users who want to connect multiple screens to a device; for example, a bar with several televisions connected to one satellite receiver or when a user has a closed laptop and uses an external display as the only monitor. HDCP devices can create multiple keys, allowing each screen to operate, but the number varies from device to device; e.g., a Dish or Sky satellite receiver can generate 16 keys.[30] The technology sometimes causes handshaking problems where devices cannot establish a connection, especially with older high-definition displays.[31][32][33]
Edward Felten wrote "the main practical effect of HDCP has been to create one more way in which your electronics could fail to work properly with your TV," and concluded in the aftermath of the master key fiasco that HDCP has been "less a security system than a tool for shaping the consumer electronics market."[34]
Additional issues arise when interactive media (i.e. video games) suffer from control latency, because it requires additional processing for encoding/decoding. Various everyday usage situations, such as live streaming or capture of game play, are also adversely affected.[35]
There is also the problem that all Apple laptop products, presumably in order to reduce switching time, when confronted with an HDCP-compliant sink device, automatically enable HDCP encryption from the HDMI / Mini DisplayPort / USB-C connector port. This is a problem if the user wishes to use recording or videoconferencing facilities further down the chain, because these devices most often do not decrypt HDCP-enabled content (since HDCP is meant to avoid direct copying of content, and such devices could conceivably do exactly that). This applies even if the output is not HDCP-requiring content, like a PowerPoint presentation or merely the device's UI.[36] Some sink devices have the ability to disable their HDCP reporting entirely, however, preventing this issue from blocking content to videoconferencing or recording. However, HDCP content will then refuse to play on many source devices if this is disabled while the sink device is connected.[37]
When connecting a HDCP 2.2 source device through compatible distribution to a video wall made of multiple legacy displays the ability to display an image cannot be guaranteed.[38]