Amit Phadikar

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.

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.

Quantization Based Data Hiding Scheme for Efficient Quality Access Control of Images Using DWT via Lifting

This paper proposes a transform domain data-hiding scheme for quality access control of images. The original image is decomposed into tiles by applying n-level lifting-based discrete wavelet transformation (DWT). A binary watermark image (external information) is spatially dispersed using the sequence of number generated by a secret key. The encoded watermark bits are then embedded into all DWT-coefficients of nth-level and only in the high-high (HH) coefficients of the subsequent levels using dither modulation (DM) but without complete self-noise suppression. It is well known that due to insertion of external information, there will be degradation in visual quality of the host image (cover). The degree of deterioration depends on the amount of external data insertion as well as step size used for DM. If this insertion process is reverted, better quality of images can be accessed. To achieve that goal, watermark bits are detected using minimum distance decoder and the remaining self-noise due to information embedding is suppressed to provide better quality of image. The simulation results have shown the validity of this claim.

Roi based error concealment of compressed object based image using QIM data hiding and wavelet transform

Transmission of digital data through radio mobile channel experiences fading effect that leads to severe degradation in quality. Error concealment is a postprocessing technique to improve this quality degradation. One such algorithm is proposed here using integer wavelet, data hiding and region-of-interest (ROI) coding functionality. Threshold based image segmentation and morphological operations are used together to find ROI. Halftoning technique is then used to obtain image digest from this ROI. To restore the human interested portion of an image, the information of ROI is embedded as image digest into the region-of-background (ROB) using data hiding based on quantization index modulation (QIM). Simulation results show that the scheme provides significant performance improvement with various lost blocks in ROI without affecting the compatibility of the standard JPEG 2000 coding scheme. Performance of the proposed scheme is also tested using simulations on Rayleigh-fading wireless channel and is compared with the few other error concealment methods.

IMAGE ERROR CONCEALMENT BASED ON QIM DATA HIDING IN DUAL-TREE COMPLEX WAVELETS

Transmission of block-coded images through error-prone radio mobile channel often results in lost blocks. Error concealment (EC) techniques exploit inherent redundancy and reduce visual artifacts through post-processing at the decoder side. In this paper, we propose an efficient quantization index modulation (QIM)-based data hiding scheme using dual-tree complex wavelet transform (DTCWT) for the application of image error concealment. The goal is achieved by embedding important information (image digest) as watermark signal that is extracted from the original image itself and is used to introduce sufficient redundancy in the transmitted image. At the decoder side, the extracted image digest is used to correct the damaged regions. DTCWT offers three-fold advantages viz. (1) high embedding capacity due to inherent redundancy that leads to the better reconstruction of high volume missing data, (2) better imperceptibly after data embedding since it most closely captures human visual system (HVS) characteristics than conventional DWT and (3) better watermark decoding reliability. Simulation results duly support the claims and relative performance improvement with respect to the existing results.

M-ary QIM Data Hiding for Error Concealment of Digital Image in JPEG Pipeline

The present paper proposes a scheme for error concealment of digital images(s) using data hiding in JPEG coding pipeline. The goal is achieved by embedding a low resolution version (image-digest) of an image into itself during compression using M-ary modulation. Halftoning technique is used to obtain the image digest from the low-resolution version of the image, while near-orthogonal quantization index modulation (QIM) is used for the implementation of M-ary modulation. At the decoder, this embedded watermark is extracted and is used as a reference to conceal the transmission losses in the received image. The simulation results show that the use of M-ary modulation provides more efficient performance measure with various loss blocks than traditional QIM, without decreasing the compatibility of standard JPEG coding scheme.

Image error concealment and quality access control based on data hiding and cryptography

This paper proposes a data hiding scheme that integrates the dual purpose of error concealment and quality access control of digital image(s) in a single platform. The objective is achieved through the extraction of some important information from the original image itself followed by embedding the same in the host data as watermark which in turn increases sufficient redundancy in the transmitted image. The data embedding is done by modulating integer wavelet coefficients using quantization index modulation (QIM). The watermarked integer wavelet coefficients are then encoded using convolution coding at high code rate. Before data embedding, the important information (watermark) is also encoded with convolution coding and is encrypted using chaotic logistic mapping. The necessary information in the form of the secret key (K) is further encrypted using a public key (P) cryptology for its secret transmission to the receiver. The user who has the knowledge of the secret key (K) can decrypt the hidden information for the concealment purpose, while the users having different partial knowledge of the key (K) enjoy relative qualities of the images by partial recovery of the damaged regions. The simulation results have shown the validity of the claim. The performance of the proposed scheme is also tested in Rayleigh-fading wireless channel and compared with the few other methods.

Multibit QIM watermarking using M-ary modulation and lifting

Quantization index modulation (QIM) principle has shown superior performance in digital watermarking over spread-spectrum and low-bit(s) modulation based methods. In QIM based data hiding scheme, it is a challenging task to embed multiple bits of information into the same set of host signal samples. This work attempts to employ M-ary modulation for multibit QIM watermarking. The watermark embedding process may be divided into two phases. In the first phase, a binary watermark image is spatially dispersed using sequence of number generated by a secret key. In the second phase, host image is decomposed by integer wavelets and the encoded watermark bits are embedded into high-low (HL) and low-high (LH) subbands of DWT-coefficients using M-ary modulation. M-ary modulation is accomplished using near-orthogonal dither generated from the combination of random key, Hadamard matrix and step size. Simulation results show that robustness is increased, at the cost of increase in decoding complexity for high M-value.

Region Specific Spatial Domain Image Watermnarking Scheme

ROI (Region of Interest) in an image or video signal contains important information and attracts more attention of an image viewer. It is desirable to insert robust watermark in ROI to give better protection of digital image. This paper describes a region specific spatial domain scheme where watermark information is embedded into the most valuable area of the cover image. The regions are selected by quad tree decomposition of host image. Simulation results validate watermark embedding in the most valuable areas of the image. Simulation results also show that the proposed scheme is robust against a wide range of attacks available in StirMark 4.0 package.

A new model of QIM data hiding for quality access control of digital image

This paper proposes a data-hiding scheme for quality access control of digital images using a new model of quantization index modulation (QIM). An encoded binary watermark is embedded over N-mutually orthogonal signal points using QIM but without complete self-noise suppression. It is well known that due to insertion of external information, there will be degradation in visual quality of the host image (cover) that plays the key role in access control through reversible process. Decision variable for each bit of watermark decoding is formed from the weighted average of N-decision statistics that increases the correctness of extracted watermark bits. The self-noise is suppressed by authorized user to provide better quality image. The simulation results have shown the validity of those claims.