In this paper. the performance of ST-DM watermarking in presence of two categories of non additive attacks, such as the gain attack plus noise addition. and the quantization attack, are evaluated. The work has been de...
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ISBN:
(纸本)0819452092
In this paper. the performance of ST-DM watermarking in presence of two categories of non additive attacks, such as the gain attack plus noise addition. and the quantization attack, are evaluated. The work has been developed by assuming that the host features are independent and identically distributed Gaussian random variables, and that a minimum distance criterion is used to decode the embedded information. The theoretical bit error probabilities are derived in closed form, thus permitting to evaluate the impact of the considered attacks on the watermark at a theoretical level. The analysis is validated by means of extensive Monte Carlo simulations. Moreover, Monte Carlo simulations permitted to abandon the hypothesis of normally distributed host features, in favor of more realistic models based on a Laplacian or a Generalized Gaussian pdf. The overall result of our analysis is that ST-DM exhibits excellent performance in all cases with the only noticeable exception of the gain attack.
In this paper we study the use of an adaptive quantization step size, instead of a fixed one, for the Scalar Costa Scheme. We propose an adaptation method based on Weber's law. This allows for a more effective emb...
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ISBN:
(纸本)0819452092
In this paper we study the use of an adaptive quantization step size, instead of a fixed one, for the Scalar Costa Scheme. We propose an adaptation method based on Weber's law. This allows for a more effective embedding, which is also shown to render the watermark robust against sample value scaling. A model for the bit error probability due to the estimation of the adaptive quantization step size at the detector is derived, which provides insight in the required precision of estimating the quantization step size in the detector.
Billions of dollars allegedly lost to piracy of multimedia content have recently triggered the industry to rethink the way music and films are distributed on the Internet. As encryption is vulnerable to digital or ana...
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Billions of dollars allegedly lost to piracy of multimedia content have recently triggered the industry to rethink the way music and films are distributed on the Internet. As encryption is vulnerable to digital or analog re-recording, currently almost all copyright protection mechanisms. rely to a certain extent on watermarking. A watermark is an,imperceptive secret hidden into a host signal. In this paper, we analyze the security of multimedia copyright protection systems that use watermarks by, proposing a new breed of attacks on generic watermarking systems. A typical blind pattern matching attack relies on the observation that multi media content is often highly repetitive. Thus, the attack procedure identifies subsets of signal blocks that are similar and permutes these blocks. Assuming the permuted blocks are marked with distinct secrets, it can be shown that any watermark detector is facing a task of exponential complexity to reverse the permutations as a preprocessing step for watermark detection. In this paper, we describe the logistics of the attack and an implementation against a spread-spectrum and a quantization index modulation data hiding technology for audio signals.
A considerable amount of attention has been paid lately to a number of data hiding methods based in quantization, seeking to achieve in practice the results predicted by Costa for a channel with side information at th...
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A considerable amount of attention has been paid lately to a number of data hiding methods based in quantization, seeking to achieve in practice the results predicted by Costa for a channel with side information at the encoder. With the objective of tilling a gap in the literature, this paper supplies a fair comparison between significant representatives of both this family of methods and the former spread-spectrum approaches that make use of near-optimal ML decoding;the comparison is based on measuring their probabilities of decoding error in the presence of channel distortions. Accurate analytical expressions and tight bounds for the probability of decoding error are given and validated by means of Monte Carlo simulations. For dithered modulation (DM), a novel technique that allows us to obtain tighter bounds to the probability of error is presented. Within the new framework, the strong points and weaknesses of both methods are distinctly displayed. This comparative study allows us to propose a new technique named "quantized projection" (QP), which, by adequately combining elements of those previous approaches, produces gains in performance.
Data hiding using quantization has revealed as an effective way of taking into account side information at the encoder. When quantizing more than one host signal samples there are two choices: 1) using the Cartesian p...
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ISBN:
(纸本)0819448206
Data hiding using quantization has revealed as an effective way of taking into account side information at the encoder. When quantizing more than one host signal samples there are two choices: 1) using the Cartesian product of several one-dimensional quantizers, as made in Scalar Costa Scheme (SCS);or 2) performing vectorial quantization. The second option seems better, as rate-distortion theory affirms that higher dimensional quantizers yield improved performance due to better sphere-packing properties. Although the embedding problem does resemble that of rate-distortion, no attacks or host signal characteristics are usually considered when designing the quantizer in this way. We show that attacks worsen the performance of the a priori optimal lattice quantizer through a counterexample: the comparison under Gaussian distortion of hexagonal lattice quantization against bidimensional Distortion-Compensated Quantized Projection (DC-QP), a data hiding alternative based in quantizing a linear projection of the host signal. Apart from empirical comparisons, theoretical lower bounds on the probability of decoding error of hexagonal lattices under Gaussian host signal and attack are provided and compared to the already analyzed DC-QP method.
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