New Digital Watermarking for Few-Color Images

In this paper, we use post processing methods to compensate the bit errors occurred in watermark embedding and extracting. Forward error correction (FEC)-based and chirp-based techniques are applied to encode and shape the embedded watermark message so that even at the presence of some bit error rates (BERs) in the extracted watermark, the watermarking algorithm be able to successfully estimate the correct embedded watermark message. Repetition and Bose-Chaudhuri-Hocquenghem (BCH) codings are used as two well-known FEC schemes, and discrete polynomial transform (DPPT) and Hough-Radon transform (HRT) are utilized as two chirp detectors in chirp-based watermarking. Robustness of all the proposed post processing methods are tested for checkmark benchmark attacks, and we found that the chirp-based watermarking using the DPPT chirp detector offers the highest watermark extraction rate, and the best bit error compensation even at BERs of higher than 17%.

In this paper, we use post processing methods to compensate the bit errors occurred in watermark embedding and extracting. Forward error correction (FEC)-based and chirp-based techniques are applied to encode and shape the embedded watermark message so that even at the presence of some bit error rates (BERs) in the extracted watermark, the watermarking algorithm be able to successfully estimate the correct embedded watermark message. Repetition and Bose-Chaudhuri-Hocquenghem (BCH) codings are used as two well-known FEC schemes, and discrete polynomial transform (DPPT) and Hough-Radon transform (HRT) are utilized as two chirp detectors in chirp-based watermarking. Robustness of all the proposed post processing methods are tested for checkmark benchmark attacks, and we found that the chirp-based watermarking using the DPPT chirp detector offers the highest watermark extraction rate, and the best bit error compensation even at BERs of higher than 17%.

In recent years, with the rapid development of internet, digital data has been widely used in various science and engineering applications. But, this development has also led to several threats and attacks from the intruders. Most of the organizations are very much concerned about the Illegal copyright activities which have become a series issue. A number of copyright protection schemes have been developed in the literature. Watermarking is one of the best known methods for copyright protection. Earlier Bit Error Rate (BER) is been observed to provide good results for choosing the optimal feature region from the watermarked image. However it fails to produce more accurate image quality measures. This research work mainly focuses on a novel technique implemented based on the simulated attacking approach and the GA-based Multi Dimensional Knapsack Problem (MDKP) solving technique to select the most sufficient feature regions for robust digital image watermarking without affecting the image quality. A major limitation in existing methods is the security problems which lead to decrease in the integrity of digital watermarking scheme. With that problem, the definite optimization problems (variant problems) cannot be resolved using genetic algorithms. To focus on the above mentioned problems, the proposed work uses two approaches. Chaotic Iterative Process encryption scheme is used to solve the security problems for watermarking image. Next, the optimal feature points can be chosen from the watermarked image by Modified version of Peak Signal Noise Ratio (MPSNR). MPSNR is based on the enhanced quality measurement of which point opposes the predefined and undefined attacks. With those two approaches the PSO algorithm is employed as a search strategy for identifying an optimal feature subset. The experimental results illustrates that comparing with various well-known feature-based techniques, the proposed method shows better performance in robust and more secure digital watermarking.

This paper proposes an improved detection algorithm for spread spectrum watermark through the realization of an efficient group combined interference cancelation (GCIC) technique. First, each watermark bit is spread over N-mutually distinct points of the cover signal and the decision variable at the decoder is formed from the weighted average of N-decision statistics. Attack channel is modeled as Rayleigh distribution followed by AWGN (additive white gaussian noise). Diversity technique is then applied to form the resultant watermarked image from the weighted average of multiple copies in order to improve detection performance where WSIR (watermark signal to interference ratio) is used as weight factor to achieve low BER (bit error rate). Genetic Algorithms (GA) is used to partition embedded bits into multiple groups, namely very strong, strong, weak and very weak based on the normalized magnitudes of their decision variables. Performance of the GA based multiple group combined interference cancelation (MGCIC) for four, three and two groups with conventional interference cancelation (IC) are then reported. A significant improvement in detection performance and capacity is seen with GA based group combined interference cancelation (GCIC) relative to conventional interference cancelation (IC) at the cost of slight increase in computation complexity. Simulation results show that bit error rate (BER) for watermark decoding is reduced as the embedded bits are divided into more number of groups and optimal partitioning of these groups are made through the use of GA.

The rapid growth of digital multimedia technologies brings tremendous attention to the field of digital authentication. Digital watermarking has become widely recognized as an effective measure for copyright protection of multimedia data. The owner or the distributor of the digital images can insert a unique watermark into copies for different customers or receivers, which will be helpful to identify the source of illegal copies. In this chapter the authors present two original spatial authentication techniques for digital images. These new algorithms yield an invisible watermark that is robust to various kinds of attacks. The main principle is the utilization of a virtual (2D or 3D) graph embedded into the digital images. Then, the colors of some vertices of the virtual graph are slightly modified for obtaining the watermark. The proposed techniques modify pixels or voxels of the object by a spatial watermark insertion scheme. These techniques can be used for all kinds of digital images, color or black and white, and the new algorithms produce an invisible robust watermark. The techniques lower the computational complexity that normally rises with the traditional watermarking algorithms. This approach reduces computation and implementation complexity of the algorithms. These techniques seem to replace advantages of the transform domain techniques with those of the spatial domain techniques.

Several spread spectrum (SS) watermarking methods have been developed to optimize imperceptibility and robustness but majority of them suffer from capacity problem due to inherent limitation of spectrum spreading. Recently, a new model of optimized SS watermark system is proposed where the number of cover signal points, payload and watermark signal-to-interference ratio (WSIR) are optimized. The objective is to meet bit error rate (BER) and peak-to-average distortion (PAD) on individual watermarked signal point are to be retained within a predefined acceptable values under the constraint of a given global embedding distortion and cover size. We further modify this SS watermarking for variable embedding rate so that each host signal point allows different data hiding capacity leading to an overall improvement in payload. Genetic algorithms (GAs) is used to optimize this adaptive SS watermarking system so that better acceptable values for BER, PAD and per sample data hiding capacity can be achieved simultaneously.

Objectives: This study aims to enhance and optimize a modern communication system for high data rate transmission using Dense Wavelength Division Multiplexing (DWDM). The objectives include employing a 64-channel DWDM system, implementing different data speeds, and utilizing a dispersion compensation method. Methods: To achieve the objectives, we simulate and analyze the effects of Dispersion Compensation Fiber (DCF) in a DWDM system with 64 channels. The system employs Non-Return-to-Zero (NRZ) modulation format at varied bit rates and multiple energy levels. We propose a method for achieving data rates of 10 to 40 Gbps using NRZ modulation and Erbium-Doped Fiber Amplifier (EDFA) over a single-mode fiber transmission distance of 40 to 160 km, along with a dispersion compensation fiber of 8 to 32 km (DCF). The performance of the developed model is evaluated based on Quality Factor, Bit Error Rate (BER), Eye Height, and Threshold. These metrics are measured at two input energy levels from an optical power source, covering a communication capacity ranging from 0.625 Tbps to 2.5 Tbps. Findings: Through the simulations and analyses, we uncover the impact of dispersion and demonstrate the effectiveness of the proposed method in compensating for dispersion effects. Performance analysis of two different input transmitter power levels, -10 dBm is more efficient compared to 0 dBm input transmitter power in terms of bit error rate and quality factor. Novelty: This study presents a novel approach to improving modern communication systems by utilizing DWDM with a dispersion compensation method. The use of a 64-channel DWDM system, combined with the proposed NRZ modulation technique and dispersion compensation fiber, provides an efficient solution for achieving high data rates over long transmission distances while minimizing the effects of dispersion. The findings contribute to the advancement of communication systems for high data rate transmission. Keywords Dispersion effect, Bit Error Rate, Q-factor, Optisystem software, Erbium doped fiber amplifier

Robust watermarks are evaluated in terms of image fidelity and robustness. We extend this framework and apply reliability testing to robust watermark evaluation. Reliability is the probability that a watermarking algorithm will correctly detect or decode a watermark for a specified fidelity requirement under a given set of attacks and images. In reliability testing, a system is evaluated in terms of quality, load, capacity and performance. To measure quality that corresponds to image fidelity, we compensate for attacks to measure the fidelity of attacked watermarked images. We use the conditional mean of pixel values to compensate for valumetric attacks such as gamma correction and histogram equalization. To compensate for geometrical attacks, we use error concealment and perfect motion estimation assumption. We define capacity to be the maximum embedding strength parameter and the maximum data payload. Load is then defined to be the actual embedding strength and data payload of a watermark. To measure performance, we use bit error rate (BER) and receiver operating characteristics (ROC) and area under the curve (AUC) of the ROC curve of a watermarking algorithm for different attacks and images. We evaluate robust watermarks for various quality, loads, attacks, and images.

A coding layer robust reversible watermarking algorithm for digital image in multi-antenna system

The relation between the digital watermarking and spread-spectrum is analyzed in this paper at the beginning. Then, a spread-spectrum adaptive digital watermarking scheme based on the wavelet transform is proposed and the system for this digital watermarking algorithm based on DSP is realized. Finally, a testing on the image digital watermarking processing system by DSP is conducted. The result from the testing approves that the system is flexible and can accomplish watermark embedding and detecting.

A secure high capacity full-gray-scale-level multi-image information hiding and secret image authentication scheme via Tchebichef moments

Spread Transform Dither Modulation (STDM), a special case of Quantization Index Modulation (QIM), has been widely used in digital watermarking. STDM has good performance in robustness against re-quantization and random noise attacks, but it is largely vulnerable to the Fixed Gain Attack (FGA). In addition to digital images and videos watermarking applications, copyright protection for digital text such as Portable Document Format (PDF) has received particular attention and interest. In this paper, we modify the STDM watermarking scheme by making the quantization step dependent on the original samples during the embedding process and on the watermarked samples during the decoding process to resist the FGA attack and enhance the robustness against the Additive White Gaussian Noise (AWGN) attack and JPEG compression attack in both the spatial domain and frequency domain regardless of the source of elements used as cover work. Experimentations have been conducted distinctly on digital images and text PDF documents. The tested images were watermarked with a uniform fidelity, where SSIM is fixed to 0.982 and 0.953. Our approach achieves significant robustness against the FGA attack with an improvement of 98% in terms of Bit Error Rates (BER) compared to traditional STDM. As for the AWGN attack, an improvement of 21% is shown. The proposed method also presents robustness against a variety of filtering and geometric attacks, while preserving a high level of transparency.

Digital image watermarking or data hiding techniques must resist various attacks such as compression, noising and geometric distortion attacks. Rotation, scaling and translation (RST) in geometric distortion attacks are considered to be more challenging than other attacks. The log-polar mapping (LPM) coordinate is used to analyse the angle of rotation and ratio of scaling between the cover image and the corrupted watermarked image. However, the watermark or secret data are easily destroyed when inverse LPM is applied. Based on LPM, this paper presents a robust digital image watermarking technique. We discuss the appropriate watermark embedding locations in the LPM coordinates. The experiment results show that the proposed method has high wPSNR and low bit error rate (BER), and can withstand RST attacks.

A wavelet based watermarking algorithm for digital image protection is proposed in this paper. Different from the traditional watermarking algorithms, in this algorithm the watermark is not embedded into the source image, but father, used to derive a secret key. The secret key is generated by mixing-up the image features and the watermark kept by the rightful owner. Signification coefficients of the image after digital wavelet transformation are adopted for feature selection. The major merit of this algorithm is that the host image will not be degraded for protection purpose and the algorithm is robust against various attacks, such as image compressing, blurring and cropping. Experimental results show the effectiveness and robustness of this algorithm.

Sixteen channel wavelength-division-multiplexed passive optical network (WDM-PON) based on one Mach-Zehnder modulator and carrier suppressed return to zero differential quadrature phase-shift keying (CSRZ-DQPSK) transmitter is designed and evaluated for various bit rates (20 Gbps to 80 Gbps). The effect of changes in transmission distance with increased bit rate is also discussed and hence quality factors and bit error rates are analyzed to evaluate their performances. The relation between transmission distance, quality factor (Q factor) and bit error rate (BER) have been focused to determine optimized result.