Better security levels for broken arrows

This paper considers the security aspect of the robust zero-bit watermarking technique ‘Broken Arrows’(BA), which was invented and tested for the international challenge BOWS-2. The results of the first episode of the challenge showed that BA is very robust. Last year, we proposed an enhancement so-called AWC, which further strengthens the robustness against the worst attack disclosed during the challenge. However, in the second and third episodes of the challenge, when the pirate observes plenty of watermarked pictures with the same secret key, some security flaws have been discovered. They clearly prevent the use of BA in multimedia fingerprinting application, as suggested in. Our contributions focus on finding some counter-attacks. We carefully investigate BA and its variant AWC, and take two recently published security attacks as the potential threats. Based on this, we propose three countermeasures: benefiting from the improved embedding technique AWC; regulating the system parameters to lighten the watermarking embedding footprint; and extending the zero bit watermarking to multi-bits for further increase the security level. With this design, experimental results show that these security attacks do not work any more, and the security level is further increased.