A public verifiable copy protection technique for still images
It is well known that a digital signature scheme and digital timestamp are two well-defined security methods for copyright protection. However, these techniques are not suitable for directly dealing with digital images. For this reason, digital watermarking has received considerable attention for copyright protection. Unfortunately, there are still some challenges in the proposed watermarking schemes. Here, we will introduce cryptographic tools into watermarking, in such a way that both the advantages of cryptographic tools and digital watermarking are available. The publicly verifiable property and tolerant distortion property are therefore possible. Based on this idea, a lossless and robust copyright-protection scheme, distinct from conventional watermarking techniques, is proposed. Our scheme is strong enough to resist common image processing, geometric distortions and some intentional attacks. Some of the attacks are still challenges for the proposed watermarking methods. A series of experiments are conducted to prove the robustness property. The StirMark and unZign attacks are adopted as benchmark verification.