Glossary
What Is High-bandwidth Digital Content Protection?
HDCP encrypts the signal on the cable between a player and a screen. It decides whether a display gets a high-quality picture, but it cannot stop a recording made after the link.
Definition
High-bandwidth Digital Content Protection (HDCP) encrypts audio and video as they travel over a digital display connection, such as HDMI or DisplayPort, between a source device and a compatible display.
What HDCP actually encrypts
HDCP covers one link: the cable between a source device, such as a set-top box, streaming stick, games console or Blu-ray player, and a sink, such as a TV, monitor or projector. Before any picture is sent, the two devices run an authentication handshake. The source checks that the sink holds valid HDCP keys and has not been revoked, then the two agree session keys and the signal is encrypted on the wire. Repeaters such as AV receivers and switches take part in the same handshake and pass the protection on.
It is easy to confuse HDCP with digital rights management. DRM decides whether a player may decrypt a film at all. HDCP only governs what happens after the player has decoded it and wants to send pictures to a screen. A title can be fully DRM-protected and still be exposed if the output link is not.
How HDCP shapes the quality a viewer gets
Streaming services and DRM licences often make the highest resolutions conditional on HDCP. If a laptop is connected to an older monitor that does not support the required version, the service may drop to a lower resolution, or the player may refuse to output protected video at all. Viewers see this as a black screen or an error saying the content cannot be played on this display. For rights holders, it is one of the controls that keeps premium-quality output away from uncontrolled hardware.
Strippers, splitters and capture rips
The weakness is well known. Inexpensive splitters and converters, some marketed for legitimate uses, accept an HDCP-protected input and output an unprotected signal. Connected to a capture card, they let someone record a pristine copy of whatever is playing, including live sport and pay-TV channels. Revocation can disable a known device's keys, but cheap hardware tends to be replaced faster than it is revoked.
That is how a clean, full-resolution copy can appear on a pirate site even when no DRM system has been compromised. The file is a capture of decoded output, often labelled as a WEBRip or HDTV capture by a release group, rather than a decrypted download.
HDCP in the evidence trail
For enforcement, the label matters less than where the copy travels next. A capture of a live channel is usually restreamed within moments; a capture of a film is uploaded to file hosts, torrent indexes and messaging channels. If the service embeds a session watermark in its output, the capture may still carry it, because stripping HDCP removes the link encryption and leaves the picture untouched. That makes watermark extraction worth attempting on any high-quality capture before the copy is removed.
- Technology
- Glossary
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