Watermark Generation using Image-dependent Key for Image Authentication

In order to increase security of the blind watermarking schemes for image authentication it is desirable to use image-dependent keys in the process of watermark generation. In this paper we propose a new watermarking method for image authentication where the watermark is generated using the image hash as a key. The robust image hash, invariant to legitimate modifications, but fragile to illegitimate modifications is generated from the local image characteristics. Due to this relation between the watermark and the image hash, it is possible to differentiate among legitimate and illegitimate modifications of the image. Quantized index modulation of DCT coefficients is used for watermark embedding. Watermark detection is performed without use of the original image. Experimental results demonstrate the effectiveness of the proposed method in terms of robustness and fragility