In data-hiding the issue of the achievable rate maximization is closely related to the problem of host interference cancellation. The optimal host interference cancellation relies on the knowledge of the host realization and the channel statistics (the additive white Gaussian noise (AWGN) variance) available at the encoder a priori to the transmission. The latter assumption can be rarely met in practical situations. Contrarily to the Costa set-up where the encoder is optimized for the particular state of the independent and identically distributed (i.i.d.) Gaussian attacking channel, we address the problem of asymmetrically informed data-hiding optimal encoder design assuming that the host interference probability density function (pdf) is an i.i.d. Laplacian and the channel variance lies on some known interval. The presented experimental results advocate the advantages of the developed embedding strategy.
In this paper, we propose a new theoretical framework for the data-hiding problem of digital and printed text documents. We explain how this problem can be seen as an instance of the well-known Gel'fand-Pinsker problem. The main idea for this interpretation is to consider a text character as a data structure consisting of multiple quantifiable features such as shape, position, orientation, size, color, etc. We also introduce <i>color quantization</i>, a new semi-fragile text data-hiding method that is fully automatable, has high information embedding rate, and can be applied to both digital and printed text documents. The main idea of this method is to quantize the color or luminance intensity of each character in such a manner that the human visual system is not able to distinguish between the original and quantized characters, but it can be easily performed by a specialized reader machine. We also describe halftone quantization, a related method that applies mainly to printed text documents. Since these methods may not be completely robust to printing and scanning, an outer coding layer is proposed to solve this issue. Finally, we describe a practical implementation of the color quantization method and present experimental results for comparison with other existing methods.
In this paper we consider the problem of document authentication in electronic and printed forms. We formulate this problem from the information-theoretic perspectives and present the joint source-channel coding theorems showing the performance limits in such protocols. We analyze the security of document authentication methods and present the optimal attacking strategies with corresponding complexity estimates that, contrarily to the existing studies, crucially rely on the information leaked by the authentication protocol. Finally, we present the results of experimental validation of the developed concept that justifies the practical efficiency of the elaborated framework.
In a data hiding communications scenario, geometrical attacks lead to a loss of reliable communications due to synchronization problems when the applied attack is unknown. In our previous work, information-theoretic analysis of this problem was performed for theoretic setups, i.e., when the length of communicated data sequences asymptotically approaches infinity. Assuming that the applied geometrical attack belongs to a set of finite cardinality, it is demonstrated that it does not asymptotically affect the achievable rate in comparison to the scenario without any attack. The main goal of this paper is to investigate the upper and lower bounds on the rate reliability function that can be achieved in the data hiding channel with some geometrical state. In particular, we investigate the random coding and sphere packing bounds in channels with random parameter for the case when the interference (channel state) is not taken into account at the encoder. Furthermore, only those geometrical transformations that preserve the input dimensionality and input type class are considered. For this case we are showing that similar conclusion obtained in the asymptotic case is valid, meaning that within the class of considered geometrical attacks the rate reliability function is bounded in the same way as in the case with no geometrical distortions.
In this paper we introduce and develop a framework for document interactive navigation in multimodal databases. First, we analyze the main open issues of existing multimodal interfaces and then discuss two applications that include interaction with documents in several human environments, i.e., the so-called smart rooms. Second, we propose a system set-up dedicated to the efficient navigation in the printed documents. This set-up is based on the fusion of data from several modalities that include images and text. Both modalities can be used as cover data for hidden indexes using data-hiding technologies as well as source data for robust visual hashing. The particularities of the proposed robust visual hashing are described in the paper. Finally, we address two practical applications of smart rooms for tourism and education and demonstrate the advantages of the proposed solution.
In digital media transfer, geometrical transformations desynchronize the communications between the encoder and the decoder. Therefore, an attempt to decode the message based on the direct output of the channel with random geometrical state fails. The main goal of this paper is to analyze the conditions of reliable communications based on structured codebooks in channels with geometrical transformations. Structured codebooks include codewords that have some features or statistics designed for synchronization purposes. In the design of capacity approaching data-hiding codes, host interference problem should be resolved. The solution to this problem is to perform the message coding based on random binning dependent on host-state. On the other hand, to achieve robustness to geometrical transformations, the codewords should have host independent statistics and encoding should be performed using random coding. To satisfy these conflicting requirements we propose Multiple Access Channel (MAC) framework where the message is split between two encoders designed based on the random binning and random coding principles. The message encoded according to random coding additionally serves for synchronization purposes. Sequentially, all existing methods that are proposed for reliable communications in channels with geometrical transformations are analyzed within the proposed MAC set-up. Depending on the particular codebook design, we classify these methods into two main groups: template-based codebooks and redundant codebooks. Finally, we perform the analysis of security leaks of each codebook structure in terms of complexity of the worst case attack.