A New Spread Spectrum Watermarking Method with Self-Synchronization Capabilities
Among the many techniques available for information concealment, those based on spread spectrum modulations have proven to yield improved results when robustness against attack is at a premium. In this paper, we propose a new spread spectrum-based watermarking procedure that combines space and frequency marks to provide good robustness properties against both spatial (affine) and transform-based compression attacks, without needing the original image as a reference (blind detection). It provides a mechanism for N-bit concealment and also improves the detection-of-presence process by gathering all watermark energy into a single value (sufficient statistic for detection). The recovery of every single bit is also improved by taking into account the so-called "watermark-print" or "waterprint" instead of looking at a single correlation value. It additionally provides the means to recover synchronization under affine transformations in the blind detection scenario. These characteristics will be analyzed by means of several practical examples.