Watermark Bits Research Articles

An IWT based blind and robust image watermarking scheme using secret key matrix

In this paper, the authors have proposed a binary watermark embedding approach for protecting the copyright ownership of the gray-scale images. The proposed watermark embedding process is realized in integer wavelet transform (IWT) domain to defend the robustness property. Instead of inserting the watermark bits directly in the coefficients of cover media, an indirect embedding mechanism is proposed with the reference to a logistic map based secret key matrix which enhance the secrecy of the proposed embedding approach. Initially, the approximate sub band of the IWT transformed cover image is selected with the intention to embed the watermark. Later, a secret key matrix of size corresponding to the approximate sub band of the cover image is formed using the logistic map with secret parameters. During the watermark embedding process, the approximate sub band is modified indirectly with reference to the secret key matrix and a proposed division table. The scheme is tested on a set of standard images and satisfactory results are achieved. In addition, the proposed schemes is also able to extract the watermark information in blind manner. Also, the scheme is comparable with some other related schemes. Finally, the proposed watermarking scheme is able to survive the watermark even after performing certain types of image manipulation attacks.

LWT–DSR based new robust framework for watermark extraction under intentional attack conditions

This paper proposes a new watermarking approach using dynamic stochastic resonance (DSR) based tuning operation to extract the watermark logo from the watermarked image that has undergone different intentional and signal processing attacks. This method is intended to provide remedies from the shortcomings of the technique proposed by Lin et al. (2008), and invalidates the effect of intentional attacks recently designed by Meerwald et al. (2009). The algorithm incorporates three level image decomposition using lifting wavelet transform (LWT) and low-pass subband is utilized for data hiding purpose. Watermark bits are embedded into the blocks of non-overlapped wavelet coefficients of the cover image by quantizing the two maximum coefficients of the corresponding block. In watermark extraction process, the DSR is applied by performing the tuning operation on coefficient blocks of attacked watermarked image. It is a parameter dependent approach that enhances the performance of watermark extraction, where the parameters of DSR inherently depend on the image properties such as standard deviation or variance. As far as security is concerned, the randomization of wavelet coefficients, blocks, and watermark bits helps the framework to be more secure. The proposed technique is also examined against multiple watermarking attack and successfully proves its authenticity and ownership. Comparison of the proposed technique with recent techniques shows remarkable improvement in terms of robustness and security against various intentional, signal processing, and geometrical attacks.

Slantlet based hybrid watermarking technique for medical images

Watermarking techniques are widely used for copyright protection, confidentiality and integrity issues in medical field. Reversibility, robustness, embedding capacity and invisibility are the essential requirements of a watermarking technique. Cogitating the need of security for medical images, this paper proposes a reversible high embedding capacity, high image fidelity, a hybrid robust lossless data hiding technique by using both transform and spatial domains. Proposed technique alters the mean of the selected non-overlapping slantlet transformed blocks of the host image whereas RS vector considers flipping factor for data embedding. The optimum thresholds to select the blocks are calculated through PSO technique and watermark is generated by using patient details, biometric id and region of interest (ROI) blocks of host image. This watermark is further compressed by applying LZW technique and encrypted by AES as well as MD5. The watermark bits are embedded in all three RGB channels of a cover image, to increase the embedding capacity up to 3.3675 bpp. The credibility of the proposed technique in comparison with other medical watermarking techniques is evidenced through experimental results.

Robust Image Watermarking Based On Quantization Index Modulation in the DCT Domain

The main drawback of the traditional quantization index modulation (QIM) watermarking is its extreme sensitivity to scaling attack. Due to scaling have a little effect on Discrete Cosine Transform (DCT) coefficients, this paper proposed a novel robust image watermarking algorithm based on QIM in the DCT domain. In the presented scheme, the medium and low frequency DCT coefficients of host signal are divided into two parts, then the watermark bits are embedded by quantizing ratio of l p -norm of the two parts. Experimental results confirm the superiority of the proposed algorithm against common types attacks in comparison with the recently proposed scheme.

Watermark BER and Channel Capacity Analysis for QPSK-Based RF Watermarking by Constellation Dithering in AWGN Channel

Radio frequency (RF) watermarking is the technology that embeds the hidden information in the normal communication signals without extra bandwidth, which could be used to identify authentication or transmit secret information. Constellation dithering (CD) is one of the RF watermarking schemes and usually used for quadrature phase shift keying signals. In this letter, the two available CD watermarking schemes are analyzed by unified theoretical model and then a new CD scheme is proposed based on the model. All the three schemes are investigated to provide the bit-error-rate formulas for the carrier symbols and watermark bits, and the watermark channel capacities have been presented for the three schemes. The numerical analysis shows that the proposed scheme has the largest watermark channel capacity in the same inaudibility constraint.

An efficient medical image watermarking scheme based on FDCuT–DCT

In this paper, a blind medical image watermarking scheme based on Fast Discrete Curvelet Transform (FDCuT) and Discrete Cosine Transform (DCT) is proposed. FDCuT is applied on the medical image to get different frequency coefficients of its curvelet decomposition. On the high frequency curvelet coefficients of the medical image, block wise DCT is applied to get different frequency coefficients. Then mid band frequency coefficients of the medical image are modified by White Gaussian Noise (WGN) sequences according to watermark bit to get watermarked medical image. At extraction end, blind recovery of watermark data is performed by correlation of WGN sequences. The proposed scheme is tested for its effectiveness on various types of medical images such as X-ray, Ultrasound (US), Magnetic Resonant Imaging (MRI) and Computerized Tomography (CT). Result analysis shows that imperceptibility of watermarked medical image is better as PSNR is above 45dB for all types of the medical images. In addition, the robustness of the scheme is better than an existing scheme for a similar set of medical images in terms of Normalized Correlation (NC). Experimental results show that scheme is robust to geometric attacks, signal processing attacks and JPEG compression attacks. An analysis is also carried out to verify the performance of the proposed scheme to support binary watermarks with different details in it: text and logos. Moreover, the proposed scheme resulted in zero false positive rate when tested on 100 non-watermarked images.

Digital Watermarking in Color Image Based On Joint Between DCT and DWT

The massive distribution and development in the digital images field with friendly software, that leads to produce unauthorized use. Therefore the digital watermarking as image authentication has been developed for those issues. In this paper, we presented a method depending on the embedding stage and extraction stag. Our development is made by combining Discrete Wavelet Transform (DWT) with Discrete Cosine Transform (DCT) depending on the fact that combined the two transforms will reduce the drawbacks that appears during the recovered watermark or the watermarked image quality of each other, that results in effective rounding method, this is achieved by changing the wavelets coefficients of selected DWT sub bands (HL or HH), followed by applying DCT transform on the selected sub band's coefficients, this method focuses on the invisibility for the embedded watermark bits, and the quality for the watermarked image; furthermore it focuses on a subjective for the recovered watermark after extraction stage. The proposed method was evaluated by using simple image quality matrix illustrated in the results, and it was found that the proposed method provide good objective quality, the recovered watermark extracted successfully and the quality of recovered watermark are survived.

Extended Shearlet-Based Image Watermarking Algorithm Using Selective Coefficients in Horizontal Cone

In this paper, a novel image watermarking method in extended shearlet domain is proposed. Since extended discrete shearlet transform is an effective multi-scale and multi-direction analysis method, it can not only provide nearly optimal description of image content, but also explicitly decompose a given image into directional components. In the presented scheme, the extended discrete shearlet transform is first applied on the host image and extended discrete shearlet transformed subimages are studied. Then, the optimum subimages are selected using the information entropy; subsequently, the watermark bits are embedded by modifying the selective shearlet coefficients of selected subbands in horizontal cone, and scrambling and spread spectrum technique are also used in the embedding process. The experimental results demonstrate that our scheme has good imperceptibility and good robustness against common attacks, such as cropping, JPEG compression and rotation attacks.

A Robust Blind Quantum Copyright Protection Method for Colored Images Based on Owner’s Signature

Watermarking is the imperceptible embedding of watermark bits into multimedia data in order to use for different applications. Among all its applications, copyright protection is the most prominent usage which conceals information about the owner in the carrier, so as to prohibit others from assertion copyright. This application requires high level of robustness. In this paper, a new blind quantum copyright protection method based on owners’s signature in RGB images is proposed. The method utilizes one of the RGB channels as indicator and two remained channels are used for embedding information about the owner. In our contribution the owner’s signature is considered as a text. Therefore, in order to embed in colored image as watermark, a new quantum representation of text based on ASCII character set is offered. Experimental results which are analyzed in MATLAB environment, exhibit that the presented scheme shows good performance against attacks and can be used to find out who the real owner is. Finally, the discussed quantum copyright protection method is compared with a related work that our analysis confirm that the presented scheme is more secure and applicable than the previous ones currently found in the literature.

Digital Speech Watermarking Based on Linear Predictive Analysis and Singular Value Decomposition

In this paper different digital audio watermarking techniques have been proposed. Currently, more attention is given to combination of Discrete Wavelet Transform (DWT) and Singular Value Decomposition (SVD) techniques for watermarking purpose. Available DWT–SVD audio watermarking techniques cannot be applied to speech signals efficiently. However, Linear Predictive Analysis (LPA) technique can model digital speech signals (20–30 ms) in more flexible and efficient ways than DWT. In this paper, a novel digital speech watermarking technique is proposed by applying both LPA and SVD. Quantization Index Modulation (QIM) is further applied to embed the watermark bits. The experimental results show that not only time and memory were reduced significantly as compared to different DWT–SVD audio watermarking techniques, but also the proposed technique was more robust and imperceptible for speech watermarking than other DWT–SVD audio watermarking techniques.

Adjustable audio watermarking algorithm based on DWPT and psychoacoustic modeling

This paper presents a novel adjustable audio watermarking method with high auditory quality by exploiting the discrete wavelet packet transform (DWPT), psychoacoustic modeling and distortion compensated-dither modulation (DC-DM) quantization. While the DWPT is used to divide the audio frames into several frequency sub-bands, the psychoacoustic model is intergraded to determine the appropriate sub-bands for watermarking and to control the number of embedded bits in each one. Then, the DC-DM technique is used to embed the watermark bits into the appropriate DWPT coefficients. The synchronization code technique is adopted in the proposed method to withstand desynchronization attacks. In order to achieve an adjustable watermarking scheme, two regulator parameters are provided to manage the capacity-robustness trade-off. The performance of the watermarking scheme is evaluated by examining different host audio signals under various watermarking attacks. The results show excellent imperceptibility of watermarked signals with an average ODG of − 0.3. In addition, the proposed scheme provides strong robustness against the attacks with low capacity. However, high capacity (about 2500 bps) can be achieved while maintaining a reasonable robustness. A comparison with some state-of-the-art audio watermarking schemes reveals that the proposed method provides competitive results.

Effective blind speech watermarking via adaptive mean modulation and package synchronization in DWT domain

This paper outlines a package synchronization scheme for blind speech watermarking in the discrete wavelet transform (DWT) domain. Following two-level DWT decomposition, watermark bits and synchronization codes are embedded within selected frames in the second-level approximation and detail subbands, respectively. The embedded synchronization code is used for frame alignment and as a location indicator. Tagging voice active frames with sufficient intensity makes it possible to avoid ineffective watermarking during the silence segments commonly associated with speech utterances. We introduce a novel method referred to as adaptive mean modulation (AMM) to perform binary embedding of packaged information. The quantization steps used in mean modulation are recursively derived from previous DWT coefficients. The proposed formulation allows for the direct assignment of embedding strength. Experiment results show that the proposed DWT-AMM is able to preserve speech quality at a level comparable to that of two other DWT-based methods, which also operate at a payload capacity of 200 bits per second. DWT-AMM exhibits superior robustness in terms of bit error rates, as long as the recovery of adaptive quantization steps is secured.

An improved robust image watermarking method using DCT and YCoCg-R color space

Watermarking is one of the solutions to prevent unauthorized use of digital media. This solution can help the protection of ownership rights by embedding the copyright information in the intended media. In this paper, a digital image watermarking algorithm in YCoCg-R color space is proposed. Thriplet components of YCoCg-R color space have a good decorrelation and changing one component has the least impact on the two other color components. So it can be effective in increasing the robustness of watermarking against various attacks. For watermark embedding the proposed method uses Discrete Cosine Transform and its coefficients relationship. During watermark bits embedding, complexity amount of host image blocks is utilized to select the target blocks and energy value of host image blocks is used to adaptive selection of embedding strengths that it causes a very high robustness especially against JPEG compression. The Arnold transformation, also, plays an important role in increasing the security of our proposed method by scrambling the watermark. Considering the conflict among three main requirements of watermarking, including imperceptibility, robustness and capacity, the proposed method is compared with other algorithms and the results show the superior robustness of the proposed method over the other algorithms with same capacity.

An optimized high payload audio watermarking algorithm based on LU-factorization

In the field of audio watermarking, reliably embedding the large number of watermarking bits per second in an audio signal without affecting the audible quality of the host audio with good robustness against signal processing attacks is still one of the most challenging issues. In this paper, a high payload, perceptually transparent and robust audio watermarking solution for such a problem by optimizing the existing problem using genetic algorithm is presented. The genetic algorithm in this paper is used to find the optimal number of audio samples required for hiding each watermarking bit. The embedding is done using the imperceptible properties of LU (lower upper) factorization in wavelet domain. This paper addresses the robustness within perceptual constraints at high payload rate in both mathematical analysis and experimental testing by representing behavior of various attacks using attack characterization. Experimental results show that the proposed audio watermarking algorithm can achieve 1280 bps capacity at an average Signal-to-noise ratio (SNR) of 31.02 dB with good robustness to various signal processing attacks such as noise addition, filtering, and compression. In addition, the proposed watermarking algorithm is blind as it does not require the original signal or watermark during extraction. The comparison of the proposed algorithm with the existing techniques also shows that the proposed algorithm is able to achieve high payload with good robustness under perceptual constraints.

An Improved Image Watermarking Method in Frequency Domain

ABSTRACTDigital watermarking is a technique for resolving copyright law in E-Commerce. In this article a combined watermarking method based on Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT) is proposed. For embedding watermark, a cover image is decomposed by a 2-level DWT, and the HL2 subband coefficients are divided into 4 × 4 blocks, then the DCT is performed on each of these blocks. The watermark bits are embedded by predefined pattern_0 or pattern_1 on the middle band coefficients of DCT. After inserting watermark, inverse DCT is applied to each 4 × 4 blocks of HL2 subband coefficients, and inverse DWT is applied to obtain the watermarked image. For watermark extraction, the watermarked image, which may be attacked by various image attacks, is decomposed with 2-level DWT and DCT similarly as watermark embedding process, then correlation between middle band coefficients of block DCT and the predefined pattern (pattern_0 and pattern_1) is calculated to decide whether a 0 bit or a 1 bit is embedded. Genetic algorithm is used to optimize the performance of embedding and extracting parameters. Simulation results show this technique is robust against JPEG attacks and many other strong attacks.

Utilizing neighborhood coefficient correlation: a new image watermarking technique robust to singular and hybrid attacks

A new blind digital image watermarking algorithm with watermark embedded in discrete cosine transform (DCT) coefficients is presented in this paper. The proposed scheme exploits correlation between DCT coefficients in neighborhood blocks for embedding. The watermark is embedded by modifying two DCT coefficients, one pertaining to a block in which watermark bit (0 or 1) is to be embedded and the other corresponding to the selected neighborhood block. Both the selected coefficients are modified by a modification factor so that the difference between the pair of coefficients is brought to a predefined zone. This difference between two DCT coefficients is used to extract watermark. The proposed technique has been tested for different attacks like JPEG compression, rotation, cropping, filtering, gaussian noise, salt and pepper noise, histogram equalization etc. It has been observed that the scheme is highly robust not only for the above mentioned attacks used singularly, but also for different possible combinations of simultaneous attacks. A comparison of the proposed technique with some state of art existing algorithms reveals that our scheme provides better results in terms of quality of watermarked images, payload and robustness.

Efficient and robust frame-synchronized blind audio watermarking by featuring multilevel DWT and DCT

This paper presents a self-synchronizing blind audio watermarking method developed based on the distinctive features of multilevel discrete wavelet transform (MDWT) and discrete cosine transform (DCT). In the proposed design, the repetitive pattern hidden in the 11th approximation subband is used to control frame synchronization, and the wideband signal covering the first to ninth detail subbands is used to hide binary information. Tracing the zero-crossings across the extracted synchronous signal makes it possible to recalibrate frame positions and achieve synchronous watermarking on a rational dither modulation (RDM) framework. We also developed a windowed vector modulation (WVM) scheme suited for the time as well as DCT domain to enhance watermark imperceptivity. The proposed watermarking method currently achieves a payload capacity of 86 bits per second. The results of PEAQ testing confirm that the watermarked audio signal retains quality nearly indistinguishable from the original. Compared with two existing synchronized methods designed specifically to cope with playback speed modification, the proposed MDWT---DCT---RDM---WVM method demonstrates superior robustness to commonly encountered attacks. When encountering desynchronization attacks, such as cropping and resampling time-scale modification, the proposed technique is capable of retrieving the watermark bits with a high degree of accuracy.

Semifragile Speech Watermarking Based on Least Significant Bit Replacement of Line Spectral Frequencies

There are various techniques for speech watermarking based on modifying the linear prediction coefficients (LPCs); however, the estimated and modified LPCs vary from each other even without attacks. Because line spectral frequency (LSF) has less sensitivity to watermarking than LPC, watermark bits are embedded into the maximum number of LSFs by applying the least significant bit replacement (LSBR) method. To reduce the differences between estimated and modified LPCs, a checking loop is added to minimize the watermark extraction error. Experimental results show that the proposed semifragile speech watermarking method can provide high imperceptibility and that any manipulation of the watermark signal destroys the watermark bits since manipulation changes it to a random stream of bits.

Robust and Reversible Audio Watermarking by Modifying Statistical Features in Time Domain

Robust and reversible watermarking is a potential technique in many sensitive applications, such as lossless audio or medical image systems. This paper presents a novel robust reversible audio watermarking method by modifying the statistic features in time domain in the way that the histogram of these statistical values is shifted for data hiding. Firstly, the original audio is divided into nonoverlapped equal-sized frames. In each frame, the use of three samples as a group generates a prediction error and a statistical feature value is calculated as the sum of all the prediction errors in the frame. The watermark bits are embedded into the frames by shifting the histogram of the statistical features. The watermark is reversible and robust to common signal processing operations. Experimental results have shown that the proposed method not only is reversible but also achieves satisfactory robustness to MP3 compression of 64 kbps and additive Gaussian noise of 35 dB.

A Watermarking Algorithm Based on DCT and JPEG Quantization Table

In this paper, we propose a scheme of watermark embedding and extracting based on DCT transform and JPEG quantization table. Firstly, the image is divided into non-overlapping 8 × 8 blocks, and each block is transformed by DCT. Then, a pair of points with the same quantization value is selected by the JPEG quantization table in order to embed one watermark bit, and the adjustment coefficients are adaptively selected by using the visual masking property of HVS. The experimental results presented in this paper showed that our proposed algorithm is robust to JPEG compression under different quality factors.