Traitor tracing
Abstract
This chapter presents the problem of tracing traitors and the most efficient solution known, Tardos codes. Tardos codes are an application overlay to the watermarking transmission layer: an identifier is generated for each user and then watermarked into a confidential document to be shared. The chapter focuses on the modeling of collusion when several traitors mix their copies. Thanks to this model, mathematics (statistics, information theory) gives us the fundamental limits of this tool.