A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> Semifragile watermarking techniques aim to prevent tam- pering and fraudulent use of modified images. A semifragile water- mark monitors the integrity of the content of the image but not its numerical representation. Therefore, the watermark is designed so that the integrity is proven if the content of the image has not been tampered with, despite some mild processing on the image. How- ever, if parts of the image are replaced with the wrong key or are heavily processed, the watermark information should indicate evi- dence of forgery. We compare the performance of eight semifragile watermarking algorithms in terms of their miss probability under forgery attack, and in terms of false alarm probability under nonma- licious signal processing operations that preserve the content and quality of the image. We propose desiderata for semifragile water- marking algorithms and indicate the promising algorithms among existing ones. © 2004 SPIE and IS&T. (DOI: 10.1117/1.1633285) <s> BIB001 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> This paper proposes a novel fragile watermarking scheme capable of perfectly recovering the original image from its tampered version. In the scheme, a tailor-made watermark consisting of reference-bits and check-bits is embedded into the host image using a lossless data hiding method. On the receiver side, by comparing the extracted and calculated check-bits, one can identify the tampered image-blocks. Then, the reliable reference-bits extracted from other blocks are used to exactly reconstruct the original image. Although content replacement may destroy a portion of the embedded watermark data, as long as the tampered area is not too extensive, the original image information can be restored without any error. <s> BIB002 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> A novel semi-fragile watermarking scheme in DWT domain for image authentication and tamper localization is proposed in this paper. The proposed scheme extracts content-based image features from the approximation subband in the wavelet domain to generate the watermark. Then the watermark is embedded into the middle frequency subband in the wavelet domain. For image authentication and tamper localization, the extracted watermark is compared with the extracted content-based image feature matrix. Experimental results show that the proposed scheme is robust to common content-preserving image processing (such as lossy JPEG compression, noise-adding), while it is fragile to malicious tamper in images. In addition, the proposed scheme can detect the tamper location accurately. <s> BIB003 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> In this paper, we propose a novel self-recovery watermarking scheme based on dual-redundant-ring structure (DRRS). All blocks of target image form a ring in a manner that the watermark of an image block is hidden in 1-LSB (least significant bit) of its next block N"1, and the copy of this watermark is embedded into 2-LSB of another block whose position is determined by the position of N"1. The validity of test image block is determined by comparing the number of inconsistent blocks in the block-neighborhood with that of its mapping block. Other detection result is generated in the same way comparing test block with copy block of its next block. The fusion of two detection marks improves tamper detection accuracy, while two copies of watermark provide a second chance for tamper recovery. Experimental results demonstrate that the proposed algorithm is superior to the state of the art of tamper detection and tamper recovery and could keep high security strength. <s> BIB004 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> In this paper, we present a new fragile watermarking method aimed at providing improved tampering localisation and self-recovery capabilities. First, a secure block-wise mechanism, resilient to cropping, is used to localise distorted blocks of pixels. Subsequently, the tampering localisation accuracy is refined by means of an iterative pixel-wise mechanism, which estimates the original watermarked pixels in altered regions. Extensive tests, using a large data-set, are presented to show to what extent the size of the tampered area influences the performance of our method. Moreover, results show that the proposed scheme compares favourably with a method presented in recent literature, in terms of tampering localisation and self-recovery performance. In fact, we show that our method is capable of partially reconstructing a cover image when 5% of its total number of pixels has been cropped. <s> BIB005 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> Digital Watermarking is a technique to embed additional data in digital images, without affecting the original image quality. It has become a useful tool for copyright protection, content authentication and steganography. Least Significant Bit is a commonly used technique in digital image watermarking. It is straight forward to understand and implement, and is widely used in many watermarking algorithms. A common problem of spatial LSB implementation is that a usual image compression can render watermark useless. In this paper we propose an alternative watermarking technique based on spatial LSB modification. It is robust against moderate JPEG compression, while keeping all the features of LSB. <s> BIB006 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> In this paper, we present the performance analysis of a self-recovery fragile watermarking scheme using block-neighbor- hood tamper characterization. This method uses a pseudorandom sequence to generate the nonlinear block-mapping and employs an optimized neighborhood characterization method to detect the tampering. Performance of the proposed method and its resistance to malicious attacks are analyzed. We also investigate three optimization strategies that will further improve the quality of tamper localization and recovery. Simulation results demonstrate that the proposed method allows image recovery with an acceptable visual quality (peak signal-to-noise ratio (PSNR) as 25 dB) up to 60% tampering. <s> BIB007 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> Protection of medical images using watermarking is an imperative area of research. In telemedicine, medical images are exchanged between distant places through unsecure networks like internet for diagnosis purpose. During this transfer, medical images may be tampered intentionally or accidentally. The medical practitioner has to check the integrity of Region of Interest (ROI) in the received medical image before making any diagnostic decisions. In this paper, we are developing a novel fragile and block based medical image watermarking technique for producing high quality watermarked medical images, verifying the integrity of ROI, detecting accurately the tampered blocks inside ROI using both average and variance of blocks and recovering the original ROI with zero loss. In the proposed method, the medical image is segmented into three sets of pixels: ROI pixels, Region of Non Interest (RONI) pixels and border pixels. Then, authentication data and information of ROI are embedded in border pixels. Recovery data of ROI is embedded into RONI. Results of experiments conducted on number of medical images reveal that proposed method produces high quality watermarked medical images, identifies the presence of tampers inside ROI of watermarked medical images with 100% accuracy and recovers the original ROI without any loss. <s> BIB008 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> This paper describes an image tamper detection and recovery method based on self-embedding dual watermarking. The watermark in the proposed method is a down-sampled version of an original image (cover image). Two identical watermarks are then decomposed into bit planes and embedded into the least-significant bit (LSB) plane of the cover image. This dual watermarking strategy ensures a robust performance in image tamper detection and recovery. Moreover, since the bit planes of the two identical watermarks are arranged in center-point-symmetric manner, image information is spread uniformly. This makes it possible to recover large area of tampering, such as, left, right, upper, or lower half of the cover image. Experimental results show that the proposed method is remarkably effective for detecting and recovering local image tampering, such as, image collage. <s> BIB009 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Embedding method: spatial domain <s> The paper proposes a modified self-embedding watermarking scheme of the Fan Chen & Hongjie He [4] that improves the quality of the recovered image. The watermarking bits are of variable length that best approximates 5 MSB of the pixel values of a 2 × 2 block of original image compared to average intensity of the block. There are 7 different schemes that help to calculate the watermarking bits for a 2 × 2 block, including the average intensity of the block. That is, when the watermarking bits of a 2 × 2 block survive an attack, the greatest deviation of the recovered block from the original block is not greater than the deviation when the block is recovered using its average intensity. Thus the PSNR between the original and recovered image is relatively higher compared with the one when image recovery used only the average intensity of the block. The experimental results confirm this fact. <s> BIB010
Several watermarking schemes designed for the detection and recovery of image tampers have been proposed as shown in Table 2 . In spatial domains, two watermarks are generated from the sender's side, i.e. detection bits and recovery bits. On the decoder side for the authentication phase BIB006 BIB001 , the watermark component is extracted to check whether there are any malicious modifications or not. If there is a tampered image, the watermark can be used to determine the tampered part, most papers using spatial domains with block-neighbourhood based  . The important thing that needs to be underlined is the selection of watermark components for recovery bit will determine the success of the recovery process. In addition, the more watermarks are inserted, the more information about verification and recovery can be maintained. Therefore, more watermarks generally result in more accurate tamper detection and improved image recovery quality. However, the number of watermarks should be selected while still protecting the image from serious distortion. Therefore, we must choose simultaneously between improving the accuracy of tamper detection and the quality of the recovered image, while preserving the image quality that watermarks should be considered in future studies BIB006 . Sreenivas BIB010 uses a self-embedding watermarking scheme that improved the quality of the restored image. This scheme compares the use of the average intensity of blocks with watermarking bits in varying lengths. Kiatpapan BIB009 uses a dual watermarking approach to ensure better image tamper detection and recovery performance. In this case, setting the bit-plane watermark is also worth noting. In the proposed Kiatpapan's method, two sets of 8-bit watermark components are arranged in symmetric centre mode so that the image information with higher information values is evenly distributed. This method, therefore, can recover the image tamper perfectly even on the left, right, up or down of the original image. In addition, the needs of authenticity inspection and correctness of the content of an image have developed fragile watermarking scheme BIB007 BIB002 . The method was developed by Wang et al. BIB003 by dividing the image into blocks of a certain size, and then the watermark is inserted into each block. The weakness of this method lies in the resistance to various attacks. Furthermore, some fragile watermarking methods have been used with the addition of better restoration capabilities and can be applied in different types of images BIB004 BIB005 BIB003 BIB008  . Research conducted by Lin et al.  facilitates the ability to detect tamper hierarchically, where this process can locate areas damaged up to three levels. If it is not found in the first level, it will continue to the second and third level as illustrated in Fig. 9 . However, in this scheme, it is not possible to recover the damaged block when the watermark that is inserted into another block is also damaged and there is no second chance to recover the block. The problem of other opportunities for restoration has been proposed by BIB005 BIB003 , for the recovery of the block was assigned to solve the accidental problem of interference by installing two copies of the restoration bits into the image. Increasing the watermarking capacity leads to a quality decrease of watermarked images as seen in Li et al. BIB004 , which uses 3 bits of the LSB to store bit recovery. To improve the quality of watermarked images and restoration of damaged images, Qin et al.  use fragile watermarking methods using adaptive bit allocation mechanisms and image improvements. This method inserts a watermark into one LSB with the ability to change the length of the block image encoding results based on the smoothness of the block. On the side of the decoder, if the extraction of the watermark length is not suitable, it cannot show where the image is damaged; some additions of authentication bit components can degrade the image quality itself. Another method BIB003 ignores the image content, removes the concealment space and uses the watermark component of the encoding result of 11 first quantisation coefficients. Huo et al.  propose a method that divides the image into eight sections according to its roughness level. The watermark component consists of authentication and recovery bits with a length that can be changed. This method can result in the precision of the destructed location. From the description of some of the methods above, the problem of fragile watermarking methods lies in the ability of restoration, i.e. in the case of watermark insertion, tamper localisation and recovery. There is a trade-off between image watermark quality and insertion capacity. The success of the fragile watermarking method is seen from the accuracy of localisation tamper. By utilising more bits to detect the damaged area, the quality of the watermarked image is reduced. Another method in  proposes the use of restoration bits to locate damaged areas but does not need to be embedded in watermarked images. The next problem is the ability of self-recovery. This process will restore the damaged area by extracting the effective information by using more bits to represent the restoration bit  . From the description above, on the sender side, the selection of watermark components is instrumental in the process of damage detection and image recovery. At the receiving end, the watermark can be extracted and can be used to cover the damaged part by using the restoration bit with the appropriate contents.