Hidden messages in heavy-tails: DCT-domain watermark detection using alpha-stable models

Efficient blind decoders for additive spread spectrum embedding based data hiding

“…The modified SS embedding scheme (11) and the vector e defined in (12) reveal that, for those coefficients where e i > 0, the watermarked signal becomes r i = x i , meaning that the coefficient r i does not convey information directly. However, because of the structure of the optimal decoder, which will be derived shortly, such r i 's still could help for decoding.…”

“…As summarized in [12], depending on different purposes, there are two main types of watermarking schemes: In one type, the embedded watermark is used to communicate a specific hidden message (e.g., binary identification numbers used for image tracking and for video distribution, or a secret hidden message represented by binary sequences) which must be extracted with sufficient decoding accuracy. In the other type of systems, the goal is only to verify whether a specific embedded watermark (e.g., representing copyright information) is presented or not, and the embedded watermark normally does not communicate a secret message that needs to be accurately decoded.…”

“…Based on the above two types of watermarking schemes, current researches on watermark extraction can be categorized into two broad topics: watermark decoding [12,13,19] for the case of decoding the hidden message and watermark detection [16][17][18][20][21][22] for the case of detecting the presence of a specific watermark. Although watermark detection and decoding problems seem to be similar from the hypothesis testing point of view, they actually serve different goals and thus different criteria are used.…”

A Robust Procedure for Image Watermarking based on the Hermite Projection Method

“…Generally, transform domain watermarking provides higher robustness to attacks. For instance, in order to improve robustness to quantization attacks, especially in the case of JPEG compression, the block-based DCT has been commonly employed [6], [7].…”

A lightweight rao-cauchy detector for additive watermarking in the dwt-domain

“…◮ host signal coefficients (DCT, DWT) modeled by GGD [Hernández et al, 2000] ◮ host signal coefficients (DCT) modeled by Cauchy distribution [Briassouli et al, 2005] ◮ LRT is optimal, but assumes that watermark power is known ◮ Using Rao test ◮ GGD host model [Nikolaidis and Pitas, 2003] ◮ Rao test makes no assumption on watermark power, but is only asymptotically equivalent to the GLRT ◮ GGD parameter estimation is computationally expensive Distribution of DWT detail subband coefficients ◮ GGD model known to fit DCT AC and DWT detail subband coefficients ◮ GGD parameters expensive to compute ◮ Often set GGD shape parameter to fixed value (eg. 0.5 or 0.8 for DCT/DWT coefficients)…”