An efficient DCT based fingerprinting scheme for thwarting collusion attacks

Many watermarking schemes are developed to protect different types of media like text, image, audio and video. Different kinds of attacks have been launched to produce illicit copies of media. Collusion attack is one of the most powerful attacks against watermarking in general and fingerprinting in particular. This paper presents an efficient scheme for hiding a logo based fingerprint in still coloured images. The scheme is inherently collusion attack resistant. It is based on averaging the middle band coefficients of block Discrete Cosine Transform (DCT) on an image. This method is compared with the conventional middle band coefficient exchange algorithm. This paper shows the robustness of the scheme against different kinds of linear and non-linear collusion attacks. In all the methods, fingerprint logo is extracted. A higher efficiency in terms of robustness is achieved in contrast with the middle band exchange scheme.