Clara Cruz-Ramos

Image Authentication Scheme Based on Self-embedding Watermarking

This paper presents a block-wise and content-based semi-fragile image watermarking authentication scheme with location and recovery capability. Firstly the image is segmented by two regions: Region of Interest (ROI) and Region of Embedding (ROE). The watermark sequence is extracted from ROI and it is embedded into the middle frequency band of DCT coefficients of ROE. In the authentication stage, two watermark sequences extracted ROI and ROE, respectively, are used. If difference between both sequences of a ROI block is smaller than the predefined threshold value, the ROI block is determined authentic, otherwise the block is considered as tampered and it is recovered by the recovery process. The proposed scheme is evaluated from several points of view: watermark imperceptibility, capability of tamper detection, image quality of recovered regions and robustness of no-intentional manipulations, such as JPEG compression. The simulation results show fairly good performance of the proposed scheme.

Watermarking Algorithm based on the DWT

Watermarking is considered as a desirable alternative for copyright protection of digital materials such as images, video and audio. Two kinds of watermarking algorithms are usually used: the watermarking algorithms using pseudorandom patterns and those using visual recognizable patterns. The main advantage of watermarking algorithms embedding a visual recognizable pattern, which can be the owner or provider logotype, is that after the extraction process the pattern can be visually recognized and then identified. In general the visual recognizable patterns has a large impact and less ambiguity during the copyright claim process as compared with the random patterns, however the amount of information required by the visual recognizable pattern is much larger than the amount of information required by the pseudorandom one, and then to achieve imperceptibility and robustness of the watermark is more difficult. This paper proposes a discrete wavelet transform (DWT) based watermark embedding algorithm for visual recognizable pattern which uses the relation between the human visual system and the DWT for embedding the watermark is such way that it becomes imperceptible and robust. Evaluation results show the desirable features of proposed scheme.

Visible Watermarking Technique Based on Human Visual System for Single Sensor Digital Cameras

In this paper we propose a visible watermarking algorithm, in which a visible watermark is embedded into the Bayer Colour Filter Array (CFA) domain. The Bayer CFA is the most common raw image representation for images captured by single sensor digital cameras equipped in almost all mobile devices. In proposed scheme, the captured image is watermarked before it is compressed and stored in the storage system. Then this method enforces the rightful ownership of the watermarked image, since there is no other version of the image rather than the watermarked one. We also take into consideration the Human Visual System (HVS) so that the proposed technique provides desired characteristics of a visible watermarking scheme, such that the embedded watermark is sufficiently perceptible and at same time not obtrusive in colour and grey-scale images. Unlike other Bayer CFA domain visible watermarking algorithms, in which only binary watermark pattern is supported, proposed watermarking algorithm allows grey-scale and colour images as watermark patterns. It is suitable for advertisement purpose, such as digital library and e-commerce, besides copyright protection.

Adaptive removable visible watermarking technique using dual watermarking for digital color images

This paper proposes a removable visible watermarking system based on a dual watermark technique and blind removal. A visible watermark pattern is embedded in the cosine discrete transform (DCT) domain, taking into consideration the texture and luminance features of the watermark and host images to create a visible watermarked image. To prevent illegal visible watermark removal, the original watermark is embedded in an invisible manner in the visible watermarked image by employing the Quantization Index Modulation-Dither Modulation (QIM-DM) technique, thus ensuring that the original watermark cannot be obtained by malicious attacks. The visible watermark removal process is carried out using only the correct user’s keys, without the need for additional information, such as the original watermark or the original host image, which allows a high-quality image to be obtained; however, if the user’s keys used in the removal process are wrong, the visible watermarked image suffers higher distortion in its content, even in non-visible watermarked regions. The experimental results show that the proposed system outperforms previous related works in terms of blind removal, preservation of the quality of the unmarked recovered image, and higher visual degradation of the content in the recovered image if an illegal removal attempt is performed.

LSB-steganography framework for stereoscopic images based on BJND

Nowadays, stereoscopic images are commonly used for 3D image generation, these are composed by a pair of images viewed independently by each eye, which creates a feeling of immersion and in depth perception. 3D vision technologies have multiple applications in many different areas such as medicine, entertainment, computer vision, etc.; being accessible to a wider group of people. However, there is so few researches that seek to hide information in this type of 3D content. This paper proposes a new method to hide information into stereoscopic images using a LSB-Steganography technique and a Binocular Just Noticeable Difference model (BJND) embedding the maximum payload capacity avoiding visual artifacts and inaccurate 3D generation. Results demonstrate that it is possible to embed up to 1.87 Mb into the stereoscopic images keeping high imperceptibility, obtaining average values for PSNR and SSIM between the original stereoscopic pair and the modified of 31.12dB and 0.9693, respectively. Quantity Bad Pixels (QBP, δd= 0. 5) and SSIM are calculated for evaluating accurate 3D generation, obtaining average values of 41.26% and of 0.7721 between the ground-truth and the disparity map of the modified stereoscopic pair.

Parallel steganography framework for hiding a color image inside stereo images

In this work, a robust steganography framework to hide a color image into a stereo images is proposed. The embedding algorithm is performed via Discrete Cosine Transform (DCT) and Quantization Index Modulation-Dither Modulation (QIM-DM) hiding the secret data. Additionally, the Arnold’s Cat Map Transform is applied in order to scramble the secret color image, guaranteeing better security and robustness of the proposed system. Novel framework has demonstrated better performance against JPEG compression attacks among other existing approaches. Besides, the proposed algorithm is developed taking into account the parallel paradigm in order to be implemented in multi-core CPU increasing the processing speed. The results obtained by the proposed framework show high values of PSNR and SSIM, which demonstrate imperceptibility and sufficient robustness against JPEG compression attacks.

Parallel halftoning technique using dot diffusion optimization

In this paper, a novel approach for halftone images is proposed and implemented for images that are obtained by the Dot Diffusion (DD) method. Designed technique is based on an optimization of the so-called class matrix used in DD algorithm and it consists of generation new versions of class matrix, which has no baron and near-baron in order to minimize inconsistencies during the distribution of the error. Proposed class matrix has different properties and each is designed for two different applications: applications where the inverse-halftoning is necessary, and applications where this method is not required. The proposed method has been implemented in GPU (NVIDIA GeForce GTX 750 Ti), multicore processors (AMD FX(tm)-6300 Six-Core Processor and in Intel core i5-4200U), using CUDA and OpenCV over a PC with linux. Experimental results have shown that novel framework generates a good quality of the halftone images and the inverse halftone images obtained. The simulation results using parallel architectures have demonstrated the efficiency of the novel technique when it is implemented in real-time processing.

Watermarking algorithm for authentication and self-recovery of tampered images using DWT

Nowadays the use of digital images is a common practice worldwide, they are used for social, commercial or legal purposes among others; therefore it is important to detect malicious alterations in this type of content, to avoid possible social, legal or personal damages. Currently there are various proposed techniques to solve this problem. However, most of these proposals can only protect a region of interest within digital image, making feasible even with these methods, the alteration of certain regions that are not protected. Therefore, this paper proposes a digital image watermarking algorithm, which consists of two stages; the first one is to protect the digital image that is performed by Daubechies DWT, halftoning and QIM methods; the second one is used for authentication, detection and self-recovery of tampered regions, through IDWT, inverse halftoning and median filtering. Experimental results have demonstrated the effectiveness of the proposed algorithm, obtaining average PSNR values of 35 dB in the self-recovery image, even if the watermarked image was subjected to a JPEG compression using a quality factor QF=75.