Watermark Estimation Research Articles

Digital Watermarking

The paper introduces the digital watermarking technology which is a data hiding technique that embeds a message into a multimedia work such as an image or text or other digital object. The proposed technique has several important applications; the majorly important is the digital copyrights protection. The digital watermarking system as any other data hiding technique has its own requirements that make the digital watermark strong as possible. Technologies of digital watermarking are mainly classified depending on their domain to spatial domain watermarks, Watermarks belonging to frequency (transform) domain and wavelet domain watermarks. The digital watermarks suffer from different types of attacks that include either state-of-the-art watermarking attacks or watermark estimation attacks. The recovery from these attacks requires strong detection techniques; the digital watermark agent provides a professional solution for these attacks.

Spread spectrum audio watermarking based on perceptual characteristic aware extraction

This study presents a high-performance audio watermarking scheme using spread spectrum modulation. Unlike conventional extractors which use simple correlation, this watermarking scheme exploits the perceptual characteristic of the watermarked audio before correlation. It is noted that although the watermark extractor works blindly neither which the original audio signal nor the embedded watermark signal is available, however, the spectral power structure of embedded watermark can be estimated using perceptual analysis methods. With this information, the watermark performance is improved by introducing an estimation-equalisation-correlation based extraction mechanism. The pre-equaliser at the extractor is carefully designed to obtain optimised extraction performance. Moreover, the perceptual analysis and shaping method are improved to make sure the watermark estimation is accurate. The perceptual characteristic aware extraction-based watermarking scheme achieves high embedding capacity up to 43 bps/channels, with low perceptual distortion to the host audio. Experiments on real audio signals show that the proposed watermarking scheme achieves high performance and is robust against various types of attacks.

Imperceptible and Robust Blind Video Watermarking Using Chrominance Embedding: A Set of Approaches in the DT CWT Domain

Illegal distribution of a digital movie is a significant threat to the film industries. With the advent of high-speed broadband Internet access, a pirated copy of a digital video can be easily distributed to a global audience. Digital video watermarking is a possible means of limiting this type of digital distribution. In existing watermarking methods, the watermark is usually embedded into the luminance channel of a video frame, which affects imperceptibility. In addition, none of the existing techniques are robust to the combination of commonly used attacks, such as compression, upscaling, rotation, cropping, downscaling in resolution, frame rate conversion, and camcording. In this paper, we initially propose a basic blind digital video watermarking algorithm, where the watermark is embedded into one level of the dual-tree complex wavelet transform of the chrominance channel to provide high quality watermarked video and extracted using the same key that was used for embedding. This algorithm is robust to compression, upscaling, rotation, and cropping. An extension of this method extracts the watermark from any level(s) of the dual-tree complex wavelet transform depending on the resolution of the downscaled version of the watermarked frame rather than only from the embedding level to survive downscaling to an arbitrary resolution. Finally, the watermark of a frame is extracted from the information of that frame without using the key that was used during watermark embedding to provide robustness to temporal synchronization attacks, such as frame rate conversion. This scheme is also robust to compression, camcording, watermark estimation remodulation, temporal frame averaging, multiple watermark embedding, downscaling in resolution, and other geometric attacks, such as upscaling, rotation, and cropping.

A new robust information hiding method for video

A new method for information hiding in digital video is presented in this paper. The proposed method is based on multi-bit frame-by-frame information hiding technique and does not require a temporal synchronization during blind information extraction. This means, proposed method provides hidden information robustness against both malicious and non-malicious frame dropping (temporal desynchronization). A new approach to randomized distribution of hidden information bits across the video frames was implemented to increase method’s embedding capacity compared to known video watermarking and information hiding techinques, robust again temporal desynchronization. Provided experimental results shows that proposed method provides hidden information robustness against frame cropping, frame loss and lossy compression using MPEG-4 and MJPEG algorithms. The proposed method is also highly robust against known “watermark estimation” attack aimed at estimation of hidden information without knowing the embedding key or non-watermarked video. Proposed information hiding method was also compared with Davey - MacKay “watermark code” redundand coding algorithm, which is also aimed at “frame loss” error correction. As a result, proposed method showed better code rates when used for small (up to 704 bits) message length.

Audio Watermarking Using Independent Component Analysis

This paper presents a blind watermark detection scheme for an additive watermark embedding model. The proposed estimation-correlation-based watermark detector first estimates the embedded watermark by exploiting non-Gaussian of the real-world audio signal and the mutual independence between the host-signal and the embedded watermark and then a correlation-based detector is used to determine the presence or the absence of the watermark. For watermark estimation, blind source separation (BSS) based on independent component analysis (ICA) is used. Low watermark-to-signal ratio (WSR) is one of the limitations of blind detection with the additive embedding model. The proposed detector uses two-stage processing to improve the WSR at the blind detector; the first stage removes the audio spectrum from the watermarked audio signal using linear predictive (LP) filtering and the second stage uses the resulting residue from the LP filtering stage to estimate the embedded watermark using BSS based on ICA. Simulation results show that the proposed detector performs significantly better than existing estimation-correlationbased detection schemes.

A MULTIMEDIA WATERMARKING TECHNIQUE BASED ON SVMs

In this paper we present an improved support vector machines (SVMs) watermarking system for still images and video sequences. By a thorough study on feature selection for training SVM, the proposed system shows significant improvements on computation efficiency and robustness to various attacks. The improved algorithm is extended to be a scene-based video watermarking technique. In a given scene, the algorithm uses the first h' frames to train an embedding SVM, and uses the trained SVM to watermark the rest of the frames. In the extracting phrase, the detector uses only the center h frames of the first h' frames to train an extracting SVM. The final extracted watermark in a given scene is the average of watermarks extracted from the remaining frames. Watermarks are embedded in l longest scenes of a video such that it is computationally efficient and capable to resist possible frames swapping/deleting/duplicating attacks. Two collusion attacks, namely temporal frame averaging and watermark estimation remodulation, on video watermarking are discussed and examined. The proposed video watermarking algorithm is shown to be robust to compression and collusion attacks, and it is novel and practical for SVM-applications.

Near-Optimal Watermark Estimation and Its Countermeasure: Antidisclosure Watermark for Multiple Watermark Embedding

Robustness is a critical requirement for a watermarking scheme to be practical. Current watermarking methods usually claim a certain degree of robustness against those attacks that aim to destroy a hidden watermark at the expense of degrading the quality of the media data. However, there exist watermark-estimation attack (WEA), such as the collusion attack, which can remove watermarks while making the attacked data further transparent to its original. Another kind of attack is the copy attack, which can cause protocol ambiguity within a watermarking system. The aim of this paper is to deal with the WEA, which is clever at disclosing hidden information for unauthorized purposes. To this end, we begin by gaining insight into the WEA, leading to formal definitions of optimal watermark estimation and near-perfect cover data recovery. Subject to these definitions, a new content-dependent watermark (CDW) is proposed to deal with watermark-estimation attack. Mathematical analyses and experimental results consistently verify the effectiveness of the proposed watermark estimation and recovery algorithm, and the proposed content-dependent watermark. To our knowledge, this anti-disclosure watermark is the first work that can give those multiple-redundant watermark embedding approaches resistance to both collusion and copy attacks

Real-time frame-dependent video watermarking in VLC domain

Digital watermarking is a helpful technology for providing copyright protection for valuable multimedia data. In particular, video watermarking deals with several issues, which are unique to various types of media watermarking. In this paper, these issues, including compressed domain watermarking, real-time detection, bit-rate control, and resistance to watermark estimation attacks, will be addressed. Since video sequences are usually compressed before they are transmitted over networks, we first describe how watermark signals can be embedded into compressed video while keeping the desired bit-rate nearly unchanged. In the embedding process, our algorithm is designed to operate directly in the variable length codeword (VLC) domain to satisfy the requirement of real-time detection. We describe how suitable positions in the VLC domain can be selected for embedding transparent watermarks. Second, in addition to typical attacks, the peculiar attacks that video sequences encounter are investigated. In particular, in order to deal with both collusion and copy attacks that are fatal to video watermarking, the video frame-dependent watermark (VFDW) is presented. Extensive experimental results verify the excellent performance of the proposed compressed video watermarking system in addressing the aforementioned issues.

Image tamper detection and classification using support vector machines

The use of robust watermarks for attack characterisation is an area of considerable potential which has been largely overlooked to date. The authors extend their earlier work on accurate attack characterisation using a double watermarking technique to include a larger library of attacks. It is shown that the complexity of the double watermarking technique can be reduced with only a very small performance penalty. A further reduction in the algorithm complexity can be achieved by removing the thresholding process from the watermark estimation procedure. Analysis of the nature and location of the characterisation errors for the above methods is also presented.

Attacks on digital watermarks: classification, estimation based attacks, and benchmarks

Watermarking is a potential method for protection of ownership rights on digital audio, image, and video data. Benchmarks are used to evaluate the performance of different watermarking algorithms. For image watermarking, the Stirmark package is the most popular benchmark, and the best current algorithms perform well against it. However, results obtained by the Stirmark benchmark have to be handled carefully since Stirmark does not properly model the watermarking process and consequently is limited in its potential for impairing sophisticated image watermarking schemes. In this context, the goal of this article is threefold. First, we give an overview of the current attacking methods. Second, we describe attacks exploiting knowledge about the statistics of the original data and the embedded watermark. We propose a stochastic formulation of estimation-based attacks. Such attacks consist of two main stages: watermark estimation, exploitation of the estimated watermark to trick watermark detection or create ownership ambiguity. The full strength of estimation-based attacks can be achieved by introducing additional noise, where the attacker tries to combine the estimated watermark and the additive noise to impair watermark communication as much as possible while fulfilling a quality constraint on the attacked data. With a sophisticated quality constraint it is also possible to exploit human perception: the human auditory system in case of audio watermarks and the human visual system in case of image and video watermarks. Third, we discuss the current status of image watermarking benchmarks. We present Petitcolas'(see Electronic Imaging '99: Security and Watermarking of Multimedia Content, SPIE Proc., vol.3657, San Jose, CA, 1999) Stirmark benchmarking tool. Next, we consider the benchmark proposed by the University of Geneva Vision Group that contains more deliberate attacks. Finally, we summarize the current work of the European Certimark project, whose goal is to accelerate efforts from a number of research groups and companies in order to produce an improved ensemble of benchmarking tools.