Lattice Costa schemes using subspace projection for digital watermarking

A general watermarking scheme employing lattice quantization is proposed and analyzed. This scheme is based on the equivalence of embedding in digital watermarking and transmission over so-called modulo-Λ channels. Main intention is to increase the maximum data rate which can be transmitted reliably (Shannon capacity of the scheme), tolerating a certain embedding and attack distortion. For this, a general concept of embedding in a subspace rather than the signal space itself is discussed, by which the capacity can be increased particularly for very low watermark-to-noise ratios. Numerical results show that the eight-dimensional Gosset lattice seems to be a promising compromise between achievable capacity and complexity in blind digital watermarking.