Binary forensic code for multimedia signals: resisting minority collusion attacks

Digital forensic marking is a technology to discourage unauthorized redistribution of multimedia signals by embedding a unique mark into each user's copy of the content. A powerful class of attacks on forensic marking is the collusion attack by a group of users. Recently, a new collusion attack, called the minority attack, has been proposed against forensic marking schemes with correlation-based detectors. Although this attack is not very effective on Gaussian-based forensic marking, it is quite powerful on removing the traces of users when the forensic marking is binary. In this paper, we first study the performance of an ECC-based binary forensic code under the minority attack and we model the additional processing, such as compression, applied on colluded copy as a binary symmetric channel. We confirm that the system can be defeated by a minority attack from only 3 colluders. To resist the minority attack, we propose a row-permuted binary orthogonal code to serve as the inner code for ECC-based forensic code, coupled with an adaptive detector. Experimental results show that the proposed scheme has a significantly improved resistance to a minority attack.