Counterfeiting attacks on oblivious block-wise independent invisible watermarking schemes

In this paper, we describe a class of attacks on certain block-based oblivi ous watermarking schemes. We show that oblivious watermarking techniques th at embed information into a host image in a block-wise independent fashion are vulnerable to a counterfeiting attack. Specifically, given a watermarke d image, one can forge the watermark it contains into another image without knowing the secret key used for watermark insertion and in some cases even without explicitly knowing the watermark. We demonstrate successful implem entations of this attack on a few watermarking techniques that have been pr oposed in the literature. We also describe a possible solution to this prob lem of block-wise independence that makes our attack computationally intrac table.