On multicast fingerprinting and collusion security

Intellectual property protection of multimedia is a thorny and largely unsolved problem. Despite its practical limitations, copy detection is an excellent complement to copy prevention. Fingerprinting techniques make redistributor tracing possible by relying on invisible watermarks embedded in the content sold which are unique for each particular buyer. That uniqueness of fingerprints is not easy to achieve in multicast transmission. We argue in this paper that encryption-based solutions are the most realistic option to fingerprint multicast transmission. However, the few existing encryption-based methods in the literature are vulnerable to buyer collusions. We propose an encryption-based algorithm which provides collusion security at the cost of transmitting the content twice.