Two-level fingerprinting: Stronger definitions and code constructions

We develop the concept of hierarchical fingerprinting introduced in our recent work (ISIT2009). The object of two-level fingerprinting is content protection against coalitions of t pirates in such a manner that one of the pirates can be identified exactly if t ≤ t₂ or localized to within a small group if t₂ <; t ≤ t₁, where t₁ and t₂ are parameters of the system. In this work, we require the additional property that in the latter case no innocent users are accused of belonging to the pirate coalition. We construct two-level fingerprinting codes with polynomial complexity of identification that satisfy the strong definition of hierarchical fingerprinting described above.