Keynote SSTIC 2009 – Traitor tracing in multimedia

Presentation : Teddy Furon

Definition : Combating the illegal redistribution of digital content.

In practice, this activity is aided by technology. Watermarking / Fingerprinting / Tattoo and others. For example, VoD servers modify certain blocks of movies, uniquely and invisibly, between users who request the movie.

While this method makes it possible to find the (probable) source of the leak, it does not make it possible to identify all the culprits.

Collusion For example, it's a technique to mix multiple film sources, in order to modify the hidden identifier, and reflect another user.
There are many ways in which collusion can occur, making the task of anti-collusion extremely difficult.
Many statisticians and mathematicians (including Gabor Tardos), studied the issue, and found an "obvious" solution.
Similar to Cluedo, it is possible to sum the probabilities of belonging to a given user, based on the clues found in the film (the bits found in the pirated copy).

The masking used must be robust, hidden, and imperceptible. The importance of imperceptibility in the case of film marking will be understood.
The use of very high or very low audio frequencies, or color differences, ensures this mechanism, without the user noticing.

The technology is now maturing and the majority of leaks are located with a very high probability rate (identifier recovery algorithms, including in the case of collusion, are very efficient and reliable).

The mathematical approach of this presentation could have put off most people, but the simple analogies made make it easier to understand the tracing of traitors, a problem that is highly topical for the film and music industry.