Spread Spectrum Embedding of Colluder Traceable Codeword in Multimedia

With digital multimedia distribution, intellectual property rights (IPR) are at a more risk than ever, due to the possibility of unlimited copying without fidelity loss. Encryption and copy protection mechanisms do not fully efficiently deal with the issue. Encryption usually protects the data only on the transport channel, and as soon as the data are decrypted for exhibit or playback, they can be copied. Copy protection mechanisms are difficult to realize in open systems as data are open to all. Thus, both encryption and copy protection offer only limited security. Watermarking has been proposed as a last line of defense in the protection of IPR. Watermarking methods embed information irremovably and invisibly into the host data. The watermark typically contains information about source and recipient of the distributed data. Thus, if pirated copies of the data are distributed, it can still be determined who owns the copyright and who the original, authorized recipient was. Thus, it allows tracing back illegally produced copies of the data. In the time of watermarking it is possible to assign some unique codeword to every copy to be distributed, by which it is possible to detect any alteration made to the watermarked copy. This paper presents spread spectrum watermarking of a specially designed colluder traceable codeword with help of combinatorial design in digital image.