Wavelet-based Watermarking Scheme Research Articles

Embedding Distortion Analysis in Wavelet-domain Watermarking

Imperceptibility and robustness are two complementary fundamental requirements of any watermarking algorithm. Low-strength watermarking yields high imperceptibility, but exhibits poor robustness. High-strength watermarking schemes achieve good robustness but often infuse distortions resulting in poor visual quality in host images. This article analyses the embedding distortion for wavelet-based watermarking schemes. We derive the relationship between distortion, measured in mean square error (MSE), and the watermark embedding modification and propose the linear proportionality between MSE and the sum of energy of the selected wavelet coefficients for watermark embedding modification. The initial proposition assumes the orthonormality of discrete wavelet transform. It is further extended for non-orthonormal wavelet kernels using a weighting parameter that follows the energy conservation theorems in wavelet frames. The proposed analysis is verified by experimental results for both non-blind and blind watermarking schemes. Such a model is useful to find the optimum input parameters, including the wavelet kernel, coefficient selection, and subband choices for wavelet domain image watermarking.

A Discrete Wavelet Based Watermarking Scheme for Authentication of Medical Images

The growth and emergence of telemedicine has resulted into considerable increase in the transfer of medical images between various health centers over computer networks for various purposes, such as diagnosis, clinical interpretation, and archives. The security of these images is a serious concern since these images can be manipulated during their transmission over the network. Moreover, as the authentication of the medical images is required for various legal purposes; the information security requirement specifications specified by various legislative rules must be adhered by the concerned stakeholders. In this research, a discrete wavelet-based watermarking scheme has been proposed for the authentication of medical images. The experimental results obtained have shown that the proposed scheme is a secure one and robust against various common image processing attacks.

An efficient and secure robust watermarking scheme for document images using Integer wavelets and block coding of binary watermarks

A novel, efficient and robust watermarking scheme for protection of document image contents is proposed in this work. An integer wavelet-based watermarking scheme for embedding the compressed version of the binary watermark logo has been developed for robust watermarking. At the sender side, the source document image is divided into empty and non-empty segments depending on the absence or presence of the information. Watermarking is applied for non-empty segments and thus the amount of embedding capacity is reduced. A binary watermark logo is compressed using binary block coding technique of appropriate block-size. A level-2 integer wavelet transformation is applied on the non-empty segment of the source document image. LL-sub-band of level-2 of the transformed image is subdivided into blocks of uniform size and compressed watermark bitstream is embedded into it. The compressed watermark is redundantly embedded into blocks using quantization technique. Thus, multiple copies of compressed watermark are available and each block of the source document image segment need not include the entire compressed watermark stream. At the receiver side, the extracted segments from each set of blocks are merged to obtain a single extracted bitstream. The bitstream is further decoded to get the binary watermark. The extracted and embedded watermarks are compared and authentication decision is taken based on majority voting technique. Based on the quantization step size, size of the logo and the level of wavelet transform, the watermarks are extracted without accessing the original image. The experimental results show that the proposed technique is highly robust. The performance of the proposed approach is measured in parameters Peak Signal to Noise Ratio (PSNR) and Normalized Correlation Coefficient (NCC). Results show that the proposed approach is better than the existing methods. In the proposed scheme for decompression of watermark, the level of block coding technique is the key, which provides an additional layer of security.

Novel watermarking technique based on the generalized squared interpoint distance for image copyright protection applications

Since image watermarking has become an important tool for intellectual property protection and authentication, a wavelet-based watermarking scheme for color images is proposed. The watermarking scheme is based on implementing the generalized squared interpoint distance (GSID) in designing a weighting function to be used in a spread-spectrum fashion watermarking (SSW) and is denoted as SSW-GSID. Watermark embedding process is carried out by transforming the host image into the wavelet domain. For highly robust and imperceptible embedding, watermark bits are added to the discrete wavelet transform (DWT) coefficients of all subbands after being weighted using the product of the calculated GSID values (of the host image) and the basis function amplitudes of the DWT decomposition. Experimental results have shown that SSW-GSID exhibits highly reliable extraction of the watermark from attacked images. Based on the provided experimental results, it can be observed that the proposed SSW-GSID method is robust against a wide variety of attacks. Comparison with other existing methods shows the superiority of the proposed SSW-GSID method.

Wavelet-based watermarking for color images through visual masking

In this paper, a wavelet-based watermarking scheme for color images is proposed. The watermarking scheme is based on the design of a color visual model that is the modification of a perceptual model used in the image coding of gray scale images. The model is to estimate the noise detection threshold of each wavelet coefficient in luminance and chrominance components of color images in order to satisfy transparency and robustness required by the color image watermarking technique. The noise detection thresholds of coefficients in each color component are derived in a locally adaptive fashion based on the wavelet decomposition, by which perceptually significant coefficients are selected and a perceptually lossless quantization matrix is constructed for embedding watermarks. Performance in terms of robustness and transparency is obtained by embedding the maximum strength watermark while maintaining the perceptually lossless quality of the watermarked color image. Simulation results show that the proposed scheme is more robust than the existing scheme while retaining the watermark transparency.

Adaptive blind wavelet-based watermarking technique using tree mutual differences

An adaptive blind wavelet-based watermarking scheme using tree mutual differences (ABW-TMD) is proposed by exploiting mutual differences between grouped coefficients of so-called wavelet trees. The ABW-TMD encoder adaptively searches for the bit host difference in such a manner to minimize the embedding error. The proposed ABW-TMD scheme proves its superiority in resisting against various image processing attacks as well as in reducing the computational cost when compared to other schemes. For the same watermark bit length, a 35% increase in peak signal-to-noise ratio (PSNR) can be achieved over what is possible using an earlier method. Also, when fixing the PSNR of the watermarked image, the watermark bit length can be doubled with the ability to extract the watermark, even in the presence of high JPEG/JPEG2000 compression ratios.

Filters Ranking for DWT-Domain Robust Digital Watermarking

In recent years a number of wavelet-based watermarking schemes have been proposed and exhibited improved qualities. The choice of a wavelet filter bank for a digital watermarking scheme can have a significant influence on the scheme's performance in terms of image quality and robustness. We present the results of experiments conducted using two different embedding algorithms (one blind and one nonblind) using a number of popular filter banks. The aim is to find filters that exhibit optimal performance with respect to specified requirements. The results demonstrate that the subband depth of embedding has the most significant influence on the filter bank choice. The kind of attack and the kind of embedding are also important, while marking intensity and compression ratio seem to affect the performance to a less extent. Additionally we show that out of the two embedding methods the quantization-based blind one leads to better overall results than the popular, nonblind one.

Synchronization recovery scheme in watermarking detection

Most proposed digital watermarking algorithms are sensitive to geometric attacks because the synchronization information of watermark embedding and detection is destroyed. In this letter a novel synchronization recovery scheme based on image normalization is proposed. The presented scheme does not require the original image and can be applied to various watermark systems. A wavelet-based watermarking scheme is proposed as an example and experimental results show that it is robust to geometric attacks.

Protection of wavelet-based watermarking systems using filter parametrization

We discuss wavelet filter parametrization as a means to add security to wavelet-based watermarking schemes. It turns out that our proposed scheme is resistant to unauthorized detection and unauthorized removal attacks and is equally robust as compared to the use of standard wavelet filters in case the underlying watermarking scheme is spread-spectrum based. Quantization-based watermarking techniques are not suited to be enhanced by this approach. We assess the security, quality and robustness of our approach in the light of four selected watermarking algorithms. Furthermore, we present an attack tailored to exploit a common weakness in image-adaptive watermarking and propose filter parametrization as a suitable countermeasure.