Improved Spread Transform Dither Modulation: A New Modulation Technique for Secure Watermarking

摘要

It is well known that Spread Transform Dither Modulation (STDM) is more robust to re-quantization such as JPEG compression than regular Quantization Index Modulation (QIM). However, we will show that the attacker can remove the watermark of STDM with low distortion. The approach is to firstly estimate the projection vector used at the encoder by Principal Component Analysis (PCA), and then nullify the watermarked signal's projection onto the estimated projection vector. This paper introduces a new watermarking modulation technique, which we call Improved Spread Transform Dither Modulation (ISTDM). The ISTDM's projection vector is random but can be estimated by the decoder for correct decoding. The experimental results show that the ISTDM achieves the security against the estimation of projection vector at the cost of slightly lower robustness...