Watermark detection based on error probability and its applications to video watermarking

As digital media which can be copied and edited readily without loss of quality has spread, several electronic watermarking methods used to protect copyrights and prevent illegal copying have been proposed. Electronic watermarking technology which can embed author information secretly in data consists primarily of embedding the watermark information, extracting watermark information, and verifying watermark information. Various methods have been proposed for embedding and extracting watermark information, depending on the scope of use and purpose. On the other hand, methods to verify the detected watermark information are limited, with BER (Bit Error Rate) and correlation between the extracted watermark information and the original watermark information widely used for evaluation. In contrast, in this paper, the authors propose a method to verify electronic watermarks based on probability. In the proposed method, the reliability that the original watermark information is embedded in the detected image is calculated as a probability, and then using this value, whether or not the watermark information is there is determined. The calculated value gives an evaluation value directly, one that includes the number of bits in the original watermark information. As a result, this verification method can he considered valid for use with video, in which watermarks are repeated. The authors use experiments to confirm the validity of their method by applying it to electronic watermarks for still images and video. (C) 2004 Wiley Periodicals, Inc.