Tracing Stateful Pirate Decoders

Most traitor tracing schemes in the literature assume that pirate decoders are stateless. This stateless assumption, however, is unrealistic especially in case of hardware decoders. Any tracing algorithm based on the above assumption may draw a wrong detecting conclusion. The present approach converts a tracing algorithm for stateless decoder into a tracing algorithm for stateful decoder. By employing a robust watermarking scheme, the proposed approach ensures that tracing processes and normal broadcast processes are indistinguishable for pirate decoders. This in turn allows a tracer to incriminate at least one traitor from a pirate decoder. Since the communication overhead for conversion is merely linear to the number of traitors and independent of the number of users, our approach is more efficient than the techniques in.