Channel model for watermarks subject to desynchronization attacks

Digital watermarking has been proposed for the copyright protection of multimedia documents, e.g., natural images, audio, video. One important unsolved problem in the field of digital watermarking is the synchronization of the watermark receiver after D/A-A/D conversion or local desynchronization attacks, e.g. StirMark’s random bending attack. In this paper, we present a channel model for watermark reception with non-perfect synchronization. Under the given channel model the capacity of SCS watermarking and imperfectly synchronized reception is derived. One important result is that the capacity of SCS watermarking depends on the document power as long perfect synchronization is not achieved. For realistic document-to-watermark power ratios, synchronization errors up to 10 % of the sampling interval can be accepted without too significant losses off the SCS watermark capacity.