Performance Comparison of Spatial Domain-based Watermarking Techniques

A novel image scaling based reversible watermarking scheme for secure medical image transmission

In this paper, we propose a new reversible watermarking algorithm based on additive prediction-error expansion which can recover original image after extracting the hidden data. Embedding capacity of such algorithms depend on the prediction accuracy of the predictor. We observed that the performance of a predictor based on full context prediction is preciser as compared to that of partial context prediction. In view of this observation, we propose an efficient adaptive prediction (EAP) method based on full context, that exploits local characteristics of neighboring pixels much effectively than other prediction methods reported in literature. Experimental results demonstrate that the proposed algorithm has a better embedding capacity and also gives better Peak Signal to Noise Ratio (PSNR) as compared to state-of-the-art reversible watermarking schemes.

Reversible watermarking technique can be used to protect the copyright of digital video and restore it without any distortion while extracting the watermarking information. However, for H.264/AVC streams, reversible watermarking scheme has the bottleneck for practical applications due to the intra error propagation phenomenon induced by watermark embedding. In this paper a novel decoder-based reversible watermarking algorithm with an error-drift elimination module for H.264/AVC is proposed for eliminating the error propagation, in which the watermark is embedded into some paired-coefficients of 4×4 quantized DCT block. Our experimental results have demonstrated that a good quality of watermarked video with a small increase in bit-rate while keeping high embedding capacity can be achieved in the proposed scheme.

Enforcing protection of medical content becomes a major issue of computer security. Since medical contents are more and more widely distributed, it is necessary to develop security mechanism to guarantee their confidentiality, integrity and traceability in an autonomous way. In this context, watermarking has been recently proposed as a complementary mechanism for medical data protection. In this paper, we focus on the verification of medical image integrity through the combination of digital signatures with such a technology, and especially with Reversible Watermarking (RW). RW schemes have been proposed for images of sensitive content for which any modification may affect their interpretation. Whence, we compare several recent RW schemes and discuss their potential use in the framework of an integrity control process in application to different sets of medical images issued from three distinct modalities: Magnetic Resonance Images, Positron Emission Tomography and Ultrasound Imaging. Experimental results with respect to two aspects including data hiding capacity and image quality preservation, show different limitations which depend on the watermark approach but also on image modality specificities.

This paper presents a secure and large capacity reversible watermarking scheme based on modified integer-to-integer discrete wavelet transform (iDWT) and code division multiple access (CDMA) algorithms. In this scheme, the watermark data are spread by orthogonal spreading sequence and then embedded into wavelet domain, which can only be extracted with same spreading codes and be removed after extraction to recover the original image exactly. The iDWT is modified with the method of exchanging the positions of nearby pixels to generate positive wavelet coefficients, through which the length of the spreading sequence is cut down and the embedding capacity enhanced effectively. The influence of the length of different spreading sequences on watermark capacity is discussed and optimal length of orthogonal spreading sequence is obtained to achieve balance between the watermark capacity and image distortion. Performance comparison with some state-of-art reversible watermarking schemes shows that the proposed scheme achieves higher embedding capacity while maintaining image distortion at lower level.

In the literature, robust reversible watermarking schemes (RWSs) allow the extraction of watermarks after the images have suffered attacks; however, the modified images are compromised. On the other hand, self-recovery schemes will restore the compromised regions of the images, but no secret messages are inserted in these schemes. A framework for robust reversible watermarking with signal restoration capabilities was previously proposed in the literature. This study selects four fragile reversible watermarking techniques and two self-recovery schemes to design different framework configurations. These configurations are evaluated to test the framework’s performance and determine the structure that yields better results in terms of perceptual transparency using a well-known image database as the signal input. It was found that fragile reversible watermarking schemes hold low perceptual distortion, while self-recovery schemes produce high perceptual distortion levels. The inherent characteristics of each algorithm determine, a priori, the behavior of the framework, which is approximated by a proposed equation.

Watermarking is a very important technique for protecting the authorization of digital content, such as still images, video streams, audio streams, and 3-D models. Most fragile watermarking schemes for 3-D models are not reversible. Published reversible or irreversible fragile watermarking schemes for 3-D models have many drawbacks, such as the causality problem, not being blind, or being unable to locate changed regions. To overcome these drawbacks, a reversible fragile watermarking scheme for 3-D models in spatial domain is proposed. Principal component analysis (PCA) is employed to produce the PCA coordinate system and make the system robust against similarity transformation attacks. PCA, together with a novel interval embedding technique, provide the blind reversibility of the proposed scheme. Intervals larger than a threshold and smaller than another threshold are adopted as legitimate to avoid large distortion. Moreover, experimental results show that the proposed scheme can overcome the causality, convergence, and confusion problems; provide both tampering detection and better embedding rate and requiring a small key size.

The classical threshold control of difference expansion reversible watermarking does not ensure a fine tuning of the embedding capacity and the simple partial embedding can introduce artifacts. The newly proposed two-thresholds embedding capacity control splits the image into two parts and marks them with consecutive threshold values. Intermediate capacity values between the ones provided by the thresholds are obtained by varying the ratio between the two parts. The method ensures a fine control of the capacity without introducing artifacts. This paper proposes a lower distortion version of the two-thresholds embedding reversible watermarking scheme. Experimental results are provided.

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

11 - Data Security and Protection for Medical Images

Overflow problem is essential to reversible watermarking algorithms, as it would lead to great distortion or irreversibility if not properly handled. In general, the existing algorithms handle overflow problem with methods that take a lot changes to pixels, which consequently brings a possibly poor quality or a high complexity. In order to solve the overflow problem specifically with a higher quality and a lower complexity, and improve the security of watermark, we put forward a new reversible watermarking scheme. We take the strategy of twice embedding-first, the proposed scheme uses wavelet histogram shifting to embed the watermark information; second, a proposed low-distortion overflow processing algorithm (LDOPA) is implemented to process the overflow problem occurred during the first step, which iteratively scans the pixels, modifies the overflow pixels one by one, and embeds the modification record with its authentication information on the image. In addition, we apply logistic mapping, torus mapping, and CRC to improve the security of the watermark, allowing users to extract watermark only when they hold the correct password. The experimental results prove that the scheme realizes the complete reversibility of watermark and carrier image. Especially, the proposed LDOPA can be easily combined with the existing watermarking methods to further improve their performance.

Medical images have been used as one of the objects to diagnose the patient. A digitally formatted medical image is easier to be stored and distributed but also easier to be modified for illegal purposes. Digital image watermarking offers a solution to protect digital medical images. By embedding fragile authentication watermark, the watermarking system can detect and localize the tampered area of medical images. Moreover, by embedding the feature extraction in the form of average intensities of the image, an original image can be recovered from the tampered image. This paper will study and test a watermarking scheme using LSB Modification to perform tamper detection and recovery in the ROI. To make this watermarking scheme reversible, RLE is used to embed the original LSBs in the RONI to get higher embedding capacity. The experimental results show that this watermarking system can detect and localize tamper with up to 100% accuracy and perform image recovery up to 100% recovery rate until 20% of tempered area in ROI.

In data hiding, pixel-value differencing and least significant bit are well-known techniques to embed secret data. In this paper, a novel data hiding scheme is proposed to provide high embedding capacity. In case of previous methods, pixel-value differencing and least significant bit techniques were used individually or in combination based on pixel, but the proposed method utilizes first by dividing the bit region and two schemes are used simultaneously in the same bit plane. The experimental results show that the proposed method has strength on embedding capacity maintaining visual image quality without distortion to the human eyes.

Reversible watermarking has drawn extensive attentions in recent years due to its broad applications of digital forensics and data security. This paper proposes a novel reversible watermarking approach, which has the perfect reversibility of the embedded data and the original image. In order to increase the embedding capacity, the proposed approach utilizes the enhanced local prediction to reduce the prediction error of every pixel value. Different from traditional reversible watermarking algorithms considering all the image pixels equivalently before prediction, an enhanced image is first computed by multiplying the original image with its saliency map. By linearly formulating each pixel value in an original image as a weighted sum of the enhanced pixel values in its local neighborhood, the correlation coefficients as learned weights are then solved as a least squares solution. Based on two state-of-the-art datasets, the experimental results show that the proposed approach achieves large embedding capacity with relatively low visual distortion.

Compared with the wide research on reversible watermarking scheme for raster image, the research on its counterpart for 2-D CAD engineering graphics lags far behind. In this paper, based on improved quantization index modulation (IQIM) and improved difference expansion (IDE), a combined reversible watermarking scheme is proposed for 2-D CAD engineering graphics. The proposed scheme can solve the embedding-limitation problem existing in IQIM technique and increase the watermark embedding capacity greatly. Theoretical analysis and experimental results also show that the proposed scheme has good imperceptibility and robustness.