Security issues have almost been ignored during the first decade of digital watermarking. As a result, many released watermarking algorithms are weak against hostile intelligence. For instance, block replacement attacks defeat watermarking systems which do not consider the self-similarities of the host signal during embedding. Such attacks replace each signal block with another one, or a combination of other ones, taken at a different location. In this paper, a novel strategy will be presented to generate a signal coherent watermark to achieve immunity against block replacement attacks. The basic idea consists in imposing a linear relationship between watermark samples embedded at different locations, with respect to their local neighborhoods which are characterized with Gabor features.