Sviatoslav Voloshynovskiy
University of Geneva
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Featured researches published by Sviatoslav Voloshynovskiy.
information hiding | 1999
Sviatoslav Voloshynovskiy; Alexander Herrigel; Nazanin Baumgaertner; Thierry Pun
This paper presents a new stochastic approach which can be applied with different watermark techniques. The approach is based on the computation of a Noise Visibility Function (NVF) that characterizes the local image properties, identifying textured and edge regions where the mark should be more strongly embedded. We present precise formulas for the NVF which enable a fast computation during the watermark encoding and decoding process. In order to determine the optimal NVF, we first consider the watermark as noise. Using a classical MAP image denoising approach, we show how to estimate the ”noise”. This leads to a general formulation for a texture masking function, that allows us to determine the optimal watermark locations and strength for the watermark embedding stage. We examine two such NVFs, based on either a non-stationary Gaussian model of the image, or a stationary Generalized Gaussian model. We show that the problem of the watermark estimation is equivalent to image denoising and derive content adaptive criteria. Results show that watermark visibility is noticeably decreased, while at the same time enhancing the energy of the watermark.
Signal Processing | 2001
Sviatoslav Voloshynovskiy; Shelby Pereira; V. Iquise; Thierry Pun
Abstract Digital image watermarking techniques for copyright protection have become increasingly robust. The best algorithms perform well against the now standard benchmark tests included in the Stirmark package. However the stirmark tests are limited since in general they do not properly model the watermarking process and consequently are limited in their potential to removing the best watermarks. Here we propose a stochastic formulation of watermarking attacks using an estimation-based concept. The proposed attacks consist of two main stages: (a) watermark or cover data estimation; (b) modification of stego data aiming at disrupting the watermark detection and of resolving copyrights, taking into account the statistics of the embedded watermark and exploiting features of the human visual system. In the second part of the paper we propose a “second generation benchmark”. We follow the model of the Stirmark benchmark and propose the 6 following categories of tests: denoising attacks and wavelet compression, watermark copy attack, synchronization removal, denoising/compression followed by perceptual remodulation, denoising and random bending. Our results indicate that even though some algorithms perform well against the Stirmark benchmark, almost all algorithms perform poorly against our benchmark. This indicates that much work remains to be done before claims about “robust” watermarks can be made. We also propose a new method of evaluating image quality based on the Watson metric which overcomes the limitations of the PSNR.
information hiding | 2001
Shelby Pereira; Sviatoslav Voloshynovskiy; Maribel Madueno; Stéphane Marchand-Maillet; Thierry Pun
Digital image watermarking techniques for copyright protection have become increasingly robust. The best algorithms perform well against the now standard benchmark tests included in the Stirmark package. However the stirmark tests are limited since in general they do not properly model the watermarking process and consequently are limited in their potential to removing the best watermarks. Here we propose a second generation benchmark for image watermarking which includes attacks which take into account powerful prior information about the watermark and the watermarking algorithms. We follow the model of the Stirmark benchmark and propose several new categories of tests including: denoising (ML and MAP), wavelet compression, watermark copy attack, active desynchronization, denoising, geometrical attacks, and denoising followed by perceptual remodulation. In addition, we take the important step of presenting results as a function of application. This is an important contribution since it is unlikely that one technology will be suitable for all applications.
Signal Processing | 2003
Frédéric Deguillaume; Sviatoslav Voloshynovskiy; Thierry Pun
Digital watermarking appears today as an efficient mean of securing multimedia documents. Several application scenarios in the security of digital watermarking have been pointed out, each of them with different requirements. The three main identified scenarios are: copyright protection, i.e. protecting ownership and usage rights; tamper proofing, aiming at detecting malicious modifications; and authentication, the purpose of which is to check the authenticity of the originator of a document. While robust watermarks, which survive to any change or alteration of the protected documents, are typically used for copyright protection, tamper proofing and authentication generally require fragile or semi-fragile watermarks in order to detect modified or faked documents. Further, most of robust watermarking schemes are vulnerable to the so-called copy attack, where a watermark can be copied from one document to another by any unauthorized person, making these schemes inefficient in all authentication applications. In this paper, we propose a hybrid watermarking method joining a robust and a fragile or semi-fragile watermark, and thus combining copyright protection and tamper proofing. As a result this approach is at the same time resistant against copy attack. In addition, the fragile information is inserted in a way which preserves robustness and reliability of the robust part. The numerous tests and the results obtained according to the Stirmark benchmark demonstrate the superior performance of the proposed approach.
international conference on communications | 2005
Taras Holotyak; Jessica J. Fridrich; Sviatoslav Voloshynovskiy
Development of digital communications systems significantly extended possibility to perform covert communications (steganography). This recalls an emerging demand in highly efficient counter-measures, i.e. steganalysis methods. Modern steganography is presented by a broad spectrum of various data-hiding techniques. Therefore development of corresponding steganalysis methods is rather a complex problem and challenging task. Moreover, in many practical steganalysis tasks second Kerckhoffs principle is not applicable because of absence of information about the used steganography method. This motivates to use blind steganalysis, which can be applied to the certain techniques where one can specify at least statistics of the hidden data. This paper focuses on the class of supervised steganalysis techniques developed for the additive steganography, which can be described as y = f(x, s, K) = x + g(s, K), where stego image y is obtained from the cover image x by adding a low-amplitude cover image independent ((1 embedding also known as LSB matching) or cover image dependent (LSB embedding) stego signals that may be also depended on secret stego key K and the secret data s. The function g(.) represents the embedding rule.
electronic imaging | 2000
Sviatoslav Voloshynovskiy; Shelby Pereira; Alexander Herrigel; Nazanin Baumgartner; Thierry Pun
Digital image watermarking has become a popular technique for authentication and copyright protection. For verifying the security and robustness of watermarking algorithms, specific attacks have to be applied to test them. In contrast to the known Stirmark attack, which degrades the quality of the image while destroying the watermark, this paper presents a new approach which is based on the estimation of a watermark and the exploitation of the properties of Human Visual System (HVS). The new attack satisfies two important requirements. First, image quality after the attack as perceived by the HVS is not worse than the quality of the stego image. Secondly, the attack uses all available prior information about the watermark and cover image statistics to perform the best watermark removal or damage. The proposed attack is based on a stochastic formulation of the watermark removal problem, considering the embedded watermark as additive noise with some probability distribution. The attack scheme consists of two main stages: (1) watermark estimation and partial removal by a filtering based on a Maximum a Posteriori (MAP) approach; (2) watermark alteration and hiding through addition of noise to the filtered image, taking into account the statistics of the embedded watermark and exploiting HVS characteristics. Experiments on a number of real world and computer generated images show the high efficiency of the proposed attack against known academic and commercial methods: the watermark is completely destroyed in all tested images without altering the image quality. The approach can be used against watermark embedding schemes that operate either in coordinate domain, or transform domains like Fourier, DCT or wavelet.
international conference on image processing | 2001
Sviatoslav Voloshynovskiy; Frédéric Deguillaume; Thierry Pun
This paper presents an efficient method for the estimation and recovering from nonlinear or local geometrical distortions, such as the random bending attack and restricted projective transforms. The distortions are modeled as a set of local affine transforms, the watermark being repeatedly allocated into small blocks in order to ensure its locality. The estimation of the affine transform parameters is formulated as a robust penalized maximum likelihood (ML) problem, which is suitable for the local level as well as for global distortions. Results with the Stirmark benchmark confirm the high robustness of the proposed method and show its state-of-the-art performance.
electronic imaging | 2000
Martin Kutter; Sviatoslav Voloshynovskiy; Alexander Herrigel
Research in digital watermarking has progressed along two paths. While new watermarking technologies are being developed, some researchers are also investigating different ways of attacking digital watermarks. Common attacks to watermarks usually aim to destroy the embedded watermark or to impair its detection. In this paper we propose a conceptually new attack for digitally watermarked images. The proposed attack does not destroy an embedded watermark, but copies it from one image to a different image. Although this new attack does not destroy a watermark or impair its detection, it creates new challenges, especially when watermarks are used for copyright protection and identification. The process of copying the watermark requires neither algorithmic knowledge of the watermarking technology nor the watermarking key. The attack is based on an estimation of the embedded watermark in the spatial domain through a filtering process. The estimate of the watermark is then adapted and inserted into the target image. To illustrate the performance of the proposed attack we applied it to commercial and non-commercial watermarking schemes. The experiments showed that the attack is very effective in copying a watermark from one image to a different image. In addition, we have a closer look at application dependent implications of this new attack.
IEEE Transactions on Neural Systems and Rehabilitation Engineering | 2007
Julien Kronegg; Guillaume Chanel; Sviatoslav Voloshynovskiy; Thierry Pun
The information-transfer rate (ITR) is commonly used to assess the performance of brain-computer interfaces (BCIs). Various studies have shown that the optimal number of mental tasks to be used is fairly low, around 3 or 4. We propose an experimental validation as well as a formal approach to demonstrate and confirm that this optimum is user and BCI design dependent. Even if increasing the number of mental tasks to the optimum indeed leads to an increase of the ITR, the gain remains small. This might not justify the added complexity in terms of protocol design
IEEE Transactions on Information Forensics and Security | 2006
Renato Villán; Sviatoslav Voloshynovskiy; Oleksiy J. Koval; Thierry Pun
In this paper, we deal with the design of high-rate multilevel 2-D bar codes for the print-and-scan channel. First, we introduce a framework for evaluating the performance limits of these codes by studying an intersymbol-interference (ISI)-free, synchronous, and noiseless print-and-scan channel, where the input and output alphabets are finite and the printer device uses halftoning to simulate multiple gray levels. Second, we present a new model for the print-and-scan channel specifically adapted to the problem of communications via multilevel 2-D bar codes. This model, inspired by our experimental work, assumes perfect synchronization and absence of ISI, but independence between the channel input and the noise is not assumed. We adapt the theory of multilevel coding with multistage decoding (MLC/MSD) to the print-and-scan channel. Finally, we present experimental results confirming the utility of our channel model, and showing that multilevel 2-D bar codes using MLC/MSD can reliably achieve the high-capacity storage requirements of many multimedia security and management applications