Public watermarks and resistance to tampering

Public watermarks allow embedded signals to be extracted from audio and video content for a variety of purposes. One application is for copyright control, where it is envisaged that digital video recorders will not permit the recording of content that is watermarked as never copy. In such a scenario, it is important that the watermark survive both normal signal transformations and attempts to remove the watermark so that an illegal copy can be made. In this paper, we discuss to what extent a public watermark can beresistant to tampering and describe a variety of possible attacks. 1 Introduction The digital distribution of copyrighted content is attractive to content owners. However, the possibility of making an unlimited number of perfect digital copies is a serious concern. While it is acknowledged that professional piracy is unlikely to be prevented by technological means alone, it is hoped that the illegal casual copying that occurs in the home can be prevented by a combination ...