Study On Digital Fingerprinting Methods Of Compressed Multimedia Signals

Digital fingerprinting is a kind of technique to deter unauthorized redistribution of multimedia content by embedding a unique identifying signal in each legally distributed copy. The embedded fingerprint can later be extracted and used to trace the originator of an unauthorized copy. A group of users may collude and attempt to create a version of the content that cannot be traced back to any of them. As multimedia data is commonly stored and transmitted in compressed form, it is more valuable to study the digital fringerprinting methods of compressed multimedia signals.Most existing collusion-resistant fingerprinting techniques are for fingerprinting uncompressed signals. Multimedia fingerprinting mainly falls into two kinds:orthogonal fingerprinting and coded fingerprinting. This paper analyses orthogonal fingerprinting and coded fingerprinting deeply and make the comparison between them. We can see that orthogonal fingerprinting possesses higher collusion resistance than coded fingerpringting. But its detection complexity is linear with the number of users, which makes it is not competent for large user application.In this paper, coded fingerprinting is chosen as the main research object. We apply it to compressed multimedia signals to trace the originator of an unauthorized copy. To overcome the quantized nature of the host signal and the embedded fingerprint, a technique for fingerprinting compressed signals called Anti-Collusion Dither (ACD) is used, whereby a random dither signal is added to the compressed host before embedding so as to save more fingerprinting information. Research and analysis is carried out on average collusion attack and interleaving collusion attack. The result shows that average collusion resistance of coded fingerprinting is better than the interleaving collusion resistance. That is because the determinant factor of average collusion resistance is noise, but the construction of coded fingerprinting is the determinant factor for the interleaving resistance of coded fingerprinting.In order to improve the collusion resistance of coded fingerprinting for practicality, this paper studies the impact of colluders'blind behavior on the collusion resistance of coded fingerprinting by simulation. Based on the verification work, the author propose interleaving embedding scheme for coded fingerprinting whose performance surpasses the permuted subsegment embedding while the overall complexity is acceptable.