Video DRM and forensic watermarking are two technologies that protect films, shows and live sport from piracy. DRM, short for digital rights management, encrypts the video so that only the devices of paying viewers can play it. A forensic watermark is an invisible mark hidden in each viewer's copy of the video. If a copy is pirated, the mark shows whose copy it was.
How does DRM work? Before a film is released, each piece of it is locked with encryption. When a subscriber presses play, the video player asks the service's licence server for the key. The licence server first checks that the subscription is active and that the device is allowed. Only then does it send the key. The key goes to a protected part of the device, which decrypts the video and sends it straight to the screen. Neither the app nor the viewer ever sees the key.
Different devices use different DRM systems. Android phones and the Chrome browser use Google's Widevine. iPhones and Apple TVs use Apple's FairPlay. Windows devices use Microsoft's PlayReady. A streaming service must support all three. It may also limit the best quality to devices with the strongest protection. On a weaker device, the same film plays only in standard definition.
DRM has a gap. Someone can still point a camera at the screen, or capture the output with special hardware, and upload the copy. This is where the forensic watermark helps. The watermark is a pattern of tiny changes in the picture that no viewer notices. Each viewer's stream carries a different pattern. One common method prepares two slightly different versions of every short piece of video. Each viewer receives a unique sequence of the two versions, and the sequence acts as an ID number.
Take, for example, a new Malayalam film that premieres on a streaming service at midnight. By 3 am, a full copy appears on a channel in a messaging app. The service's anti-piracy team downloads a few minutes of the pirated copy. The watermark software reads the pattern and finds the account that streamed it. The service blocks the account, asks the messaging app to take the copy down, and keeps the evidence for legal action.
The same protection is used in pay TV and in cinemas, where films reach each digital cinema server encrypted. A white-label streaming platform usually includes it ready-made. In India, piracy of films is also an offence under the Cinematograph Act. The encrypted pieces are produced right after the video encoder finishes its work.