Rafiullah Chamlawi

Technical Communication: Authentication and recovery of images using multiple watermarks

A novel wavelet domain based semi-fragile watermarking scheme is presented for securing digital content and to concisely determine the regions where the integrity fails. In addition, another watermark is embedded to perform self-recovery in case of malicious attack. The security weaknesses of the traditional block-based approaches are circumvented by correlating the watermark bits with wavelet coefficients of the approximation subband of the host image. Semi-fragility exhibits robustness to JPEG compression, while recovery attribute makes the scheme suitable for video surveillance and remote sensing applications. Experimental investigations are performed to evaluate the performance of the proposed multiple semi-fragile watermarks and shows the suitability of the proposed approach for accurate authentication and recovery based applications.

Digital image authentication and recovery

Recently, several semi-fragile watermarking approaches with the additional capability of image recovery have been proposed. However, the security, robustness, and image recovery aspect of these approaches have certain shortcomings. In this paper, a novel semi-fragile watermarking framework using integer transform based information embedding and extraction is proposed, which allows accurate authentication and recovery of the image. It is based on integer wavelet transform with improved security against collage attack, enhanced robustness, and capability of producing better quality recovered image. Security is enhanced by correlating the to-be-embedded watermark with the approximation subband of wavelet transform. Similarly, no unprotected area is left for attacks on the image, either in spatial or transform domain. Robustness is enhanced by using the idea of embedding in largest coefficient inside a group and correlating it with the quantized version of the mean of the group. In particular, the recovery approach is improved by introducing lossless compression and BCH coding of the integer DCT based low-pass version of the cover image itself. Alteration sensitivity is improved compared to traditional block-based approaches and thus the proposed approach can concisely determine the regions where the integrity verification fails. Experimental comparisons with existing approaches validate the usefulness of the proposed multiple semi-fragile watermarking approach.

Intelligent reversible watermarking and authentication: Hiding depth map information for 3D cameras

In this paper, we propose an application for 3D cameras by reversibly hiding the depth map in the corresponding 2D images. The proposed technique is prospective in cameras capable of capturing simultaneously the 2D image and resultant depth map of an object. 3D cameras equipped with self-embedding capability can serve two additional purposes, protection of the captured image and secure transmission of its depth map. The reversible watermarking, in addition to other features, guarantees the lossless recovery of an original image and separation of its depth map when required. For this purpose, a reversible watermarking scheme, based on genetic algorithm (GA), has been proposed which computes suitable threshold for each block of coefficients in the wavelet domain. Thus, a tradeoff is made between watermark imperceptibility and capacity using GA. The threshold map is embedded in addition to the actual payload and thus the proposed approach does not require histogram pre-processing in order to avoid overflow/underflow. The same threshold map has been used for authentication purpose by correlating it with the low-frequency coefficients of the 2D transformed image. Further to exploit the inherent redundancy in the depth map, which is the actual payload in this case, lossless compression has been employed before its embedding. Similarly, besides secret key-based permutation, a cryptographic layer is overlaid on the watermarking layer for security purposes. Experiments conducted on images and depth maps, obtained using a 3D camera and an optical microscopic system, validate the proposed concept.

Wavelet Based Image Authentication and Recovery

In this paper, we propose a secure semi-fragile watermarking technique based on integer wavelet transform with a choice of two watermarks to be embedded. A self-recovering algorithm is employed, that hides the image digest into some wavelet subbands for detecting possible illicit object manipulation undergone in the image. The semi-fragility makes the scheme tolerant against JPEG lossy compression with the quality factor as low as 70%, and locates the tampered area accurately. In addition, the system ensures more security because the embedded watermarks are protected with private keys. The computational complexity is reduced by using parameterized integer wavelet transform. Experimental results show that the proposed scheme guarantees safety of a watermark, recovery of image and localization of tampered area.

Authentication of images for 3D cameras: Reversibly embedding information using intelligent approaches

In this work, a reversible watermarking approach for authentication of 3D cameras based on computational intelligence is presented. Two intelligent techniques based on differential evolution (DE) and hybrid DE are employed to optimize the tradeoff between watermark imperceptibility and capacity. The proposed approach is suitable for images of 3D cameras. These cameras generally work on the concept of time-of-flight and not only produce the 2D image but also generate the corresponding depth map. In this approach, the depth map is considered as secret information and is hidden in the integer wavelet transform of the corresponding 2D image. The proposed technique is prospective for authenticating 3D camera images and allows the secure transmission of its depth map. It has the advantage of the lossless recovery of original 2D image as and when needed. The watermarking of the 2D images is based on integer wavelet transform and threshold optimization. The threshold map thus obtained using the intelligent optimization approaches is not only used for watermark embedding, but is also utilized for authentication purpose by correlating it with the corresponding 2D transformed image. Experiments conducted on images and depth maps obtained using 3D camera validate the proposed concept.

Authentication and recovery of digital images: Potential application in video surveillance and remote sensing

This paper presents a semi-fragile watermarking technique capable of both authenticating and recovering an image. The proposed approach offers choice of embedding two watermarks and is able to detect and differentiate the modifications applied on the watermarked image. Semi-fragility makes the scheme tolerant against JPEG lossy compression. While, recovery attribute makes it suitable for video surveillance and remote sensing applications.

Dual watermarking method for secure image authentication and recovery

This paper presents a semi-fragile watermarking technique capable of verifying the authenticity and recovery of the image. The proposed approach has the capability to accurately detect and differentiate modifications applied on the watermarked image. Alteration sensitivity has been improved compared to previous approaches and it can concisely determine the region of the watermarked image where the integrity verification fails. Semi-fragility makes the proposed method tolerant against JPEG lossy compression and other acceptable modifications but sensitive to malicious attacks such as cutting and pasting. The exact low pass version of the image is recovered by using the lossless compression (Huffman coding). Simulation results demonstrate that the alteration sensitivity of the proposed authentication scheme is much better compared to the previous approaches.

Perceptual Shaping in Digital Image Watermarking Using LDPC Codes and Genetic Programming

In this work, we present a generalized scheme for embedding watermark in digital images used for commercial aims. Genetic Programming is used to develop appropriate visual tuning functions, in accordance with Human Visual System, which cater for watermark imperceptibility-robustness trade off in the presence of a series of probable attacks. The use of low-density parity check codes for information encoding further enhances watermark robustness. Experimental results on a dataset of test images show marked improvement in robustness, when compared to the conventional approaches with the same level of visual quality. The proposed scheme is easy to implement and ensures significant robustness for watermarking a large number of small digital images.

Towards a Better Robustness-Imperceptibility Tradeoff in Digital Watermarking

Robustness and imperceptibility are two essential but contradicting properties in robust digital watermarking. This paper proposes an approach for obtaining superior robustness-imperceptibility tradeoff by considering the likely set of attacks a watermark is expected to be mounted with. The suggested approach achieves this improvement by using Genetic Programming to develop appropriate perceptual shaping functions for structuring the watermark intelligently by choosing the optimum strength of allowable alteration in watermarkable DCT features, in view of a set of conceivable attacks. The developed perceptual shaping functions, which outperform the conventional ones, are generalized with respect to the cover work and are based on the watermark application.