Soft-decision decoding of traceability codes

In the multimedia content market, there is the need to protect both intellectual property and distribution rights against dishonest buyers. Traitor tracing schemes provide means to find the guilty party in the case of an illegal redistribution. We consider traitor tracing schemes that use error correcting codes, where each user is assigned a unique set of ordered symbols. Since redistributing the set without modification trivially identifies the guilty user, a group of users, aiming to distort their identities, combine their sets and create a new pirate set. In this case, traitor tracing consists in identifying the users whose set agrees the most with the pirate. We present a traitor tracing algorithm that, taking advantage of soft-decision decoding techniques, finds all possibly identifiable traitors, thus extending the capabilities of previously known tracing algorithms.