Multibit quantization index modulation: A high-rate robust data-hiding method

Nowadays, the quantization index modulation (QIM) principle is popular in digital watermarking due to its considerable performance advantages over spread-spectrum and low-bit(s) modulation. In a QIM-based data-hiding scheme, it is a challenging task to embed multiple bits of information into the host signal. This work proposes a new model of QIM, i.e., the M-ary amplitude modulation principle for multibit watermarking. The watermark embedding process may be divided into two phases. In the first phase, a binary watermark image is spatially dispersed using a sequence of numbers generated by a secret key. In the second phase, the host image is decomposed by lifting, and the encoded watermark bits are embedded into the high–low (HL) and low–high (LH) subbands of DWT-coefficients using M-ary amplitude modulation. The results of the simulation show that the robustness increases, at the cost of increased decoding complexity, for a high M-value. Furthermore, this investigation has shown that the decoding complexity of higher M-values can be overcome at moderate N-values, while the robustness performance is maintained at satisfactory level.