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21 March 2005 Iterative estimation of amplitude scaling on distortion-compensated dither modulation
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Abstract
The vulnerability of quantization-based data hiding schemes to amplitude scaling has required the formulation of countermeasures to this relatively simple attack. Parameter estimation is one approach, where the applied scaling is estimated from the received signal at the decoder. As scaling of the watermarked signal creates a mismatch with respect to the quantization step assumed by the decoder, this estimate can be used to correct the mismatch prior to decoding. In this work we first review previous approaches utilizing parameter estimation as a means of combating the scaling attack on DC-DM. We then present a method for maximum likelihood estimation of the scaling factor for this quantization-based method. Using iteratively decodable codes in conjunction with DC-DM, the estimation method exploits the reliabilities provided by the near-optimal decoding process in order to iteratively refine the estimate of the applied scaling. By performing estimation in cooperation with the decoding process, the complexity of which is tackled using the expectation maximization algorithm, reliable estimation is possible at very low watermark-to-noise power ratios by using sufficiently low rate codes.
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Kevin M. Whelan, Felix Balado, Guenole C. M. Silvestre, and Neil J. Hurley "Iterative estimation of amplitude scaling on distortion-compensated dither modulation", Proc. SPIE 5681, Security, Steganography, and Watermarking of Multimedia Contents VII, (21 March 2005); https://doi.org/10.1117/12.587064
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