Santi P. Maity

Region based QIM digital watermarking scheme for image database in DCT domain

This paper proposes a region based digital watermarking scheme to serve the purpose of copyright protection and integrity verification of image database using discrete cosine transform (DCT). The objective is achieved by embedding watermark into visually significant regions of the image(s) using quantization index modulation (QIM). The main contributions of this work are, (1) the use of quad tree decomposition for image segmentation to find visually significant regions, and (2) the use of image database as a single entity for watermarking, instead of watermarking on individual image, so that integrity of the database is checked. Simulation results validate the above claims. Simulation results also show that the proposed scheme is robust and secured against a wide range of attacks available in StirMark 4.0 package.

A blind CDMA image watermarking scheme in wavelet domain

The paper proposes a blind spread spectrum watermarking scheme where watermark information is embedded redundantly in the multilevel wavelet coefficients of the cover image. It has been shown that for a given embedding distortion, data embedding in LL and HH bands offers higher resiliency through better spectrum spreading compared to LH and HL band embedding, although the security of the hidden data is better in the later case. High resiliency of the scheme is supported by the good visual quality of the watermark images extracted from the several distorted watermarked images. Data hiding capacity is increased using code division multiple access (CDMA) technique and the mutual information values for the different watermark images are able to detect the degree of distortion already occurred in the watermarked image.

Dual purpose FWT domain spread spectrum image watermarking in real time

Spread spectrum (SS) watermarking for multimedia signal becomes appealing due to its high robustness attribute and is used widely for various applications. Some of these applications essentially demand development of low cost algorithms so that they can be used for real time services such as broadcast monitoring, security in communication etc. In recent time one popular non-conventional application of digital watermarking becomes promising that assesses blindly the QoS (quality of services) of the multimedia services which is expected to be offered by the future generation mobile radio network. Majority of the existing SS watermarking schemes suffer from high computation cost and complexity leading to the difficulty for real time implementation and limits their usage for the above mentioned applications. This paper proposes fast Walsh transform (FWT) based SS image watermarking scheme that serves the dual purposes of authentication in data transmission as well as QoS assessment for digital media through dynamic estimation of the wireless channel condition. Fast Walsh transform offers low computation cost for implementation, smaller change in image (multimedia signal) information due to data embedding and ease of hardware realization. VLSI implementation using field programmable gate array (FPGA) has been developed to make it suitable for real time implementation.

Robust SS watermarking with improved capacity

Robustness is a key attribute of spread spectrum (SS) watermarking scheme. It is significantly deteriorated if one tries to achieve high embedding rate keeping other parameters unaltered. In literatures, typically various transformations like DFT, DCT, Fourier-Mellin and wavelet are used for SS multimedia watermarking but little studies have been attempted so far to see what are the possible factors which can improve robustness. The current paper has critically analyzed few such factors namely design of code pattern, proper signal decomposition suitable for data embedding, direction of decomposition, selection of regions for data embedding, signaling scheme, choice of modulation functions and embedding strength. Based on the observation, wavelet based SS watermarking scheme is proposed and improvement in robustness performance is verified through experimental results as well by mathematical analysis.

Collusion resilient spread spectrum watermarking in M-band wavelets using GA-fuzzy hybridization

This paper proposes a collusion resilient optimized spread spectrum (SS) image watermarking scheme using genetic algorithms (GA) and multiband (M-band) wavelets. M-band decomposition of the host image offers advantages of better scale-space tiling and good energy compactness. This bandpass-like decomposition makes watermarking robust against frequency selective fading-like gain (intelligent collusion) attack. On the other hand, GA would determine threshold value of the host coefficients (process gain i.e. the length of spreading code) selection for watermark casting along with the respective embedding strengths compatible to the gain of frequency response. First, a single bit watermark embedding algorithm is developed using independent and identically distributed (i.i.d) Gaussian watermark. This is further modified to design a high payload system for binary watermark image using a set of binary spreading code patterns. Watermark decoding performance is improved by multiple stage detection through cancelation of multiple bit interference (MBI) effect. Fuzzy logic is used to classify decision magnitudes in multiple group combined interference cancelation (MGCIC) used in the intermediate stage(s). Simulation results show convergence of GA and validate relative performance gain achieved in this algorithm compared to the existing works.

Energy Efficient Cognitive Radio System for Joint Spectrum Sensing and Data Transmission

An energy-efficient cognitive radio system design is suggested that simultaneously meets spectrum sensing reliability and secondary data transmission rate constraints. System model involves co-located multiple amplify-and-forward relays in single cognitive radio source-destination (S-D) environment with a primary focus on optimal relay power allocation strategy. The problem is mathematically formulated as minimization of total energy consumption under the constraints of sensing reliability (in terms of detection and false alarm probabilities), secondary user throughput and interference threshold to primary user. Then a cluster based nonequal relay power allocation is also suggested. Extensive simulation results illustrate the variation of the minimum energy consumption with the key system parameters.

Perceptually adaptive spread transform image watermarking scheme using Hadamard transform

The present paper proposes a digital image watermarking scheme using the characteristics of the human visual system (HVS), spread transform technique and statistical information measure. Spread transform (ST) scheme is implemented using the transform coefficients of both the host and the watermark signal. Watermark embedding strength is adaptively adjusted using frequency sensitivity, luminance, contrast and entropy masking of HVS model. The choice of Hadamard transform as watermark embedding domain offers several advantages, such as low loss in image information (higher image fidelity), greater reliability of watermark detection and higher data hiding capacity at high degree of compression. Performance of the proposed method is compared with a number of recently reported watermarking schemes based on spread spectrum (SS) and quantization index modulation (QIM).

Multistage Spread Spectrum Watermark Detection Technique Using Fuzzy Logic

In this letter, a new model of spread spectrum (SS) watermarking is proposed where each watermark bit is spread using a distinct code pattern over N-mutually orthogonal signal points. Decision variable for each bit of watermark decoding is formed from the weighted average of N-decision statistics. Multiple detection stages are applied where the detected bit patterns of one stage are used in the immediate subsequent stage to cancel the multiple bit interference (MBI) effect experienced by the individual bit. Fuzzy logic is used to beat the effect of such MBI through Multiple Group Combined Interference Cancelation (MGCIC) technique in the intermediate stage(s). The group is formed from the decision magnitudes corresponding to a group of code patterns and the ensemble of code patterns are classified in different groups like very strong, strong, weak and very weak based on fuzzy membership function derived from the magnitude of the decision variables. Attack channel is modeled as Rayleigh distribution followed by AWGN (additive white Gaussian noise). Simulation results show that BER (bit error rate) value is reduced more, of course, at the cost of slight increase in computational complexity if the code patterns are classified in a greater number of groups.

Novel wavelet-based QIM data hiding technique for tamper detection and correction of digital images

This paper proposes a tamper detection and correction technique using semi-fragile data hiding that aims to achieve high perceptual quality of images at the user-end even after malicious modifications. A binary signature and an image digest are embedded by modulating integer wavelet coefficients using dither modulation based quantization index modulation. Half-toning technique is used to obtain image digest from the low-resolution version of the host image itself. Decoder extracts the binary signature from the watermarked image for tamper detection, while the extracted image digest is used to correct the tamper region. Unlike previously proposed techniques, this novel approach distinguishes malicious changes from various common image processing operations more efficiently and also correct tapered regions effectively. Experimental results show that the proposed technique provides a superior performance in terms of probability of miss and false alarm as well as in tamper correction, compared to several existing semi-fragile watermarking techniques.

Genetic algorithms for optimality of data hiding in digital images

This paper investigates the scope of usage of Genetic Algorithms (GA) for data hiding in digital images. The tool has been explored in this topic of research to achieve an optimal solution in multidimensional nonlinear problem of conflicting nature that exists among imperceptibility, robustness, security and payload capacity. Two spatial domain data hiding methods are proposed where GA is used separately for (i) improvement in detection and (ii) optimal imperceptibility of hidden data in digital images respectively. In the first method, GA is used to achieve a set of parameter values (used as Key) to represent optimally the derived watermark in the form of approximate difference signal used for embedding. In the second method, GA is used for finding out values of parameters, namely reference amplitude (A) and modulation index (μ) both with linear and non linear transformation functions, for achieving the optimal data imperceptibility. Results on robustness for both the methods against linear, non linear filtering, noise addition, and lossy compression as well as statistical invisibility of the hidden data are reported here for some benchmark images.