What is Forensic Watermarking?

Forensic watermarking is the process of hiding identifying information in each individual copy of a video file (read our whitepaper about the topic). A good watermark, like Custos’, is almost entirely imperceptible, impossible to remove without also damaging the host video, and secure – it cannot be faked or modified.

In the past, only the largest studios and distributors could afford forensic watermarking. Custos now makes this security technology easy to use and affordable for even the smallest video producer. The watermarking is also fast: the time-consuming video processing is done only once; after that, any number of individually watermarked copies can be created almost instantaneously.

Forensic watermarking is quickly becoming ubiquitous in the digital media rights management industry, but it is not new.

Analog watermarks date back to the 13th century, when they were first applied to paper documents. Subaudible tones used for synchronization in film strip projectors in the 1970s are an early example of audio watermarks used in other types of media. However, digital watermarking was first introduced in 1993 and was used to embed information into images. Philips launched their session-based forensic video watermark in 2007, which made it possible to embed viewer information directly in a pay-TV subscriber’s set-top box.

Since then, the use of session-based forensic watermarks has become a common way to track the source of infringed content.

The following characteristics are desirable for forensic watermarks:

  1. Imperceptibility: A forensic watermark should not be audible or visible. To a human, a forensically watermarked media object should be indistinguishable from the unwatermarked original.

  2. Robustness: Even if an attacker knows that a media object is watermarked, it should be infeasible to remove the watermark without unacceptably damaging the host media in the process.

  3. Capacity: A good forensic watermark is capable of storing a large payload, as measured in bits of information.

  4. Security: It should be infeasible for an attacker to modify the payload of the watermark, or create a falsely watermarked media object.

  5. Efficiency: It should take as little computational time as possible to embed and extract the watermark into and from a media object.

How Custos’ Forensic Watermark Works

Custos provides a session-based forensic video watermark that is specifically designed to be readable by a publicly available extractor tool.

The watermark is built to be highly imperceptible (even in high dynamic range content), robust against the most destructive attacks like heavy video compression and “cam ripping”, and very fast to embed. It also has an exceptionally high payload capacity of 256 bits.

An application called Privateer is used to extract the watermark. After the video is downloaded, Privateer scans the video file frame-by-frame and builds up the payload. Forward error correction is used to repair damage caused by potential attacks.

For a watermark to be read reliably, “video registration” needs to be performed first, which is the reversal of clipping, rotation, timescale adjustment, and other reversible transforms. Independent software tools are available to do this, and Custos’ use of “bounty hunters” who voluntarily scan for watermarked content, puts “humans in the loop” who can intelligently reverse attacks to successfully read the watermark to claim a reward.

This poses a major improvement over visible watermarking. If a copy of a movie is found online, it can be traced back to the intended recipient, and this person can be prosecuted, excluded from future distribution, or otherwise sanctioned.

The real power, however, is not as much in the tracking of infringement as in the deterrent effect that this so-called “social Digital Rights Managment (DRM)” has on would-be pirates.

This social part of the DRM that plays into the incentives of would-be pirates is also the feature that sets it apart from conventional hard DRM in terms of appeal – both to end users and rights holders.

Hard DRM attempts to block redistribution of content by technical means. This can be anything from copy protection on physical media, to web players that do not allow you to record the screen.

The problem with this approach in terms of protecting against piracy is that sophisticated pirates will always be able to circumvent it. The analog hole means that any media that is meant for human consumption can be copied.

It might be difficult, but it is possible, and only a single attacker needs to succeed at it for copies to start proliferating across the internet.

How we combine forensic watermarking with the bitcoin blockchain to protect digital content from piracy.

The Custos team has engineered a way to combine patented blockchain technology with forensic watermarking, to simplify DRM and content security workflows for media and edtech businesses.

Our online media distribution platforms and API integrations offer flexible options to host, watermark, and securely distribute video, audio, e-books, and sensitive documents.

To date, Custos’ plug-and-play distribution solutions have protected over 260 000 films, e-books, and confidential documents from copyright infringement, using cryptocurrency ─ reducing piracy by 99.97% in markets across four continents.

On the back end, the platform generates unique copies for each reviewer. In each copy, using cutting edge forensic watermarking, we embed a Bitcoin wallet.

(A Bitcoin wallet is just a special string of numbers.)

This number is not visible to a viewer, but encoded into small variations in the colour and brightness that a human eye won’t be able to see, but that will remain in the copy even if you copy or compress it.

Those variations, and the unique number – i.e. Bitcoin wallet – contained within them, are what make up our forensic watermark.

In each Bitcoin wallet there’s a bit of Bitcoin. Any one in the world that finds a copy in the wild can take this Bitcoin as their reward, and through the blockchain we are informed whose copy was found somewhere it should not have been.

Are clients affected by the volitilaty of cryptocurrency markets?

No. The nice thing about building a blockchain technology that does not rely on the price of any cryptocurrency or token is that our solution remains equally effective through the waxing and waning of the markets.

The technology is cryptocurrency agnostic, and we have experimented with Bitcoin Cash, Ethereum, ZCash and Litecoin. Using cryptocurrency and the blockchain gives us a way to decentralise the detection of pirated material. We give cryptocurrency bounties to anyone who finds a leaked copy of a movie or ebook. Each copy that is distributed contains a unique cryptocurrency wallet, and we monitor when such a wallet is emptied. We can then identify who the source of the leak was. This is something that was not possible to do before cryptocurrency on the global scale in an anonymised manner that is required to fight piracy.

Are our forensic watermarks compatible with other leading DRM tools?

Absolutely. Integrating with other DRM tools will allow you to implement a “belt-and-braces” approach where you make casual copying of your content difficult, and can still catch any copyright infringers.

Currently, we’re not actively integrated with leading DRM tools, but definitely something we’d be willing to check out if you have the need for it.

This post includes an excerpt from our latest whitepaper, Why Watermarking is not Enough: How Blockchain Technology can be Used to Stop Online PiracyClick here to download your free copy today.