A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> 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. <s> BIB001 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> This paper proposes two novel self-embedding watermarking schemes based upon a reference sharing mechanism, in which the watermark to be embedded is a reference derived from the original principal content in different regions and shared by these regions for content restoration. After identifying tampered blocks, both the reference data and the original content in the reserved area are used to recover the principal content in the tampered area. By using the first scheme, the original data in five most significant bit layers of a cover image can be recovered and the original watermarked image can also be retrieved when the content replacement is not too extensive. In the second scheme, the host content is decomposed into three levels, and the reference sharing methods with different restoration capabilities are employed to protect the data at different levels. Therefore, the lower the tampering rate, the more levels of content data are recovered, and the better the quality of restored results. <s> BIB002 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <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> BIB003 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> This paper proposes a novel watermarking scheme with flexible self-recovery quality. The embedded watermark data for content recovery are calculated from the original discrete cosine transform (DCT) coefficients of host image and do not contain any additional redundancy. When a part of a watermarked image is tampered, the watermark data in the area without any modification still can be extracted. If the amount of extracted data is large, we can reconstruct the original coefficients in the tampered area according to the constraints given by the extracted data. Otherwise, we may employ a compressive sensing technique to retrieve the coefficients by exploiting the sparseness in the DCT domain. This way, all the extracted watermark data contribute to the content recovery. The smaller the tampered area, the more available watermark data will result in a better quality of recovered content. It is also shown that the proposed scheme outperforms previous techniques in general. <s> BIB004 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <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> BIB005 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> Due to the wide variety of attacks and the difficulties of developing an accurate statistical model of host features, the structure of the watermark detector is derived by considering a simplified channel model. In this paper, we present a fragile watermarking based on block-mapping mechanism which can perfectly recover the host image from its tampered version by generating a reference data. By investigating characteristics of watermark detector, we make an effective analysis such as fragility against robustness measure and distinguish its property. In particular, we derive a watermark detector structure with simplified channel model which focuses on the error probability versus watermark-to-noise-ratio curve and describes a design by calculating the performance of technique, where attacks are either absent or as noise addition. <s> BIB006 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> This paper proposes a fragile image watermarking scheme with recover ability based on local binary pattern (LBP). The local binary pattern operator is mostly used to extract localized spatial features for texture analysis, image classification, and pattern recognition. According to spatial relations of a natural image, a local binary pattern can be utilized to represent the localized relations of a pixel with its neighborhood. Each pixel measured by the LBP operator can be obtained its own local binary pattern as representation of local spatial relations. The proposed scheme utilizes the LBP operator to generate authentication data which are embedded into each image block with 3 × 3 pixels size for tamper detection and recovery. The recovery information is obtained by calculating the mean value of each image block, and then the mean value is converted into a binary string which is embedded into eight neighboring pixels' LSBs of each image block for image recovering. From the experimental results, the proposed scheme has efficient tamper detection, better image quality and recovering ability than Zhang and Shih's LBP based watermarking scheme. <s> BIB007 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> Digital image processing technology presents new challenges for the security of the image information, which makes image authentication as a problem to be addressed. Digital watermarking plays an important role in multimedia information security. This paper proposed a dual watermarking method to do tamper location and self-recovery, which utilizes self-embedding technology to hide eigenface into the low frequence sub band LL to restore the tamper region. Experimental results show the availability of the proposed algorithm. <s> BIB008 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> Abstract The art of secretly hiding and communicating information has gained immense importance in the last two decades due to the advances in generation, storage, and communication technology of digital content. Watermarking is one of the promising solutions for tamper detection and protection of digital content. However, watermarking can cause damage to the sensitive information present in the cover work. Therefore, at the receiving end, the exact recovery of cover work may not be possible. Additionally, there exist certain applications that may not tolerate even small distortions in cover work prior to the downstream processing. In such applications, reversible watermarking instead of conventional watermarking is employed. Reversible watermarking of digital content allows full extraction of the watermark along with the complete restoration of the cover work. For the last few years, reversible watermarking techniques are gaining popularity because of its increasing applications in some important and sensitive areas, i.e., military communication, healthcare, and law-enforcement. Due to the rapid evolution of reversible watermarking techniques, a latest review of recent research in this field is highly desirable. In this survey, the performances of different reversible watermarking schemes are discussed on the basis of various characteristics of watermarking. However, the major focus of this survey is on prediction-error expansion based reversible watermarking techniques, whereby the secret information is hidden in the prediction domain through error expansion. Comparison of the different reversible watermarking techniques is provided in tabular form, and an analysis is carried out. Additionally, experimental comparison of some of the recent reversible watermarking techniques, both in terms of watermarking properties and computational time, is provided on a dataset of 300 images. Future directions are also provided for this potentially important field of watermarking. <s> BIB009 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> Fragile watermarking is discovered for authentication and content integrity verification. This paper introduces a modified fragile watermarking technique for image recovery. Here we can detect as well as recovered the tampered image with its tampered region. This modified approach helps us to produce resistance on various attacks like birthday attack, college attack and quantization attacks. Using a non-sequential block chaining and randomized block chaining, which is created on the basis of secrete key this modified technique produces great amount of recovery from tampered regions. In this modified technique we put a watermark information and information of recovery of image block into the image block. These blocks are linked with next randomly generated block of image. In this modified process of block chaining to obtained first watermark image, modified technique uses original image and watermarked image. While to obtained self-embedded image we merge shuffled original image on original image so that we get final shuffled image. At last we merge first watermark image with shuffled image to produce final watermarked image. During recovery we follow reverse process of above to obtained original image from tampered image. By comparing block by block mean values of tampered blocks recovery of tampered blocks can be done. This modified technique can be used for color as well as gray scale images. The implementation shows that, the proposed modified technique can be used with promising result as an alternative approach to image recovery from tampered area effectively. <s> BIB010 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <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> BIB011 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <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> BIB012 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> DCT based effective self-recoverable fragile watermarking scheme is presented.This scheme has extreme localization and restoration capability.The blocking artifacts negligible because of using the small blocks of size 2×2.Two levels hierarchical tampered detection mechanisms are used for tampered block detection. This paper presents a Discrete Cosine Transformation (DCT) based effective self-recoverable fragile watermarking scheme. For each 2 × 2 non-overlapping block, two authentication bits, and ten recovery bits are generated from the five most significant bits (MSBs) of pixels. Authentication bits are embedded in the three least significant bits (LSBs) of the block itself while recovery bits are embedded in the three LSBs of the corresponding mapped block. The proposed watermarking scheme is also effective because the authentication of each block is based on two levels hierarchical tampered detection mechanisms. So the detection of tampered block can be ensured with high probability. The experimental results demonstrate that the proposed scheme not only outperforms high-quality restoration effectively, but also removes the blocking artifacts and improves the accuracy of tamper localization due to the use of very small size blocks, smoothing function and two levels tampering detection mechanisms. <s> BIB013 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> A novel self-embedding watermarking scheme for tampering recovery is proposed. Two types of modes, i.e., overlapping and overlapping-free embedding, are used. Flexible, MSB-based, interleaved reference bits are embedded for content recovery. Embedding modes can be adaptively chosen to achieve optimal performances. Theoretical analysis and experiments are given to show the superiority of our scheme. In this paper, we propose a novel self-embedding fragile image watermarking scheme for tampering recovery based on reference-data interleaving mechanism and adaptive selection of embedding mode. During watermark embedding, reference bits are derived from the interleaved, scrambled MSB bits of original image, and then are combined with authentication bits to form the watermark bits for LSB embedding. Different with the reported schemes with the fixed embedding mode, the proposed scheme not only has two types of embedding modes, i.e., overlapping-free embedding and overlapping embedding, but also utilizes the adaptively flexible numbers of MSB and LSB layers to achieve satisfactory performances for different tampering rates. Also, detailed analyses are given to provide the theoretical values of watermarked-image quality, perfect recovery probability, and recovered-image quality, which are used to conclude the optimal choice of embedding modes. Experimental results show the effectiveness and superiority of the proposed scheme compared with some state-of-the-arts schemes. <s> BIB014 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> Abstract In the present work, a novel image watermarking algorithm using vector quantization (VQ) approach is presented for digital image authentication. Watermarks are embedded in two successive stages for image integrity verification and authentication. In the first stage, a key based approach is used to embed robust zero level watermark using properties of indices of vector quantized image. In the second stage, semifragile watermark is embedded by using modified index key based (MIKB) method. Random keys are used to improve the integrity and security of the designed system. Further, to classify an attack quantitatively as acceptable or as a malicious attack, pixel neighbourhood clustering approach is introduced. Proposed approach is evaluated on 250 standard test images using performance measures such as peak signal to noise ratio (PSNR) and normalized hamming similarity (NHS). The experimental results shows that propose approach achieve average false positive rate 0.00024 and the average false negative rate 0.0012. Further, the average PSNR and tamper detection/localization accuracy of watermarked image is 42 dB and 99.8% respectively; while tamper localization sensitivity is very high. The proposed model is found to be robust to common content preserving attacks while fragile to content altering attacks. <s> BIB015 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> Image authentication, which is provided with capabilities of tamper detection and data recovery, is an efficient way to protect the contents of digital images. Vector quantization (VQ) is a data compression method. A VQ-compressed code is not only a significant image authentication feature but also applicable in restoring possibly damaged pixels. However, if an image is tampered with, the necessary recovery information disappears. To solve this problem, this paper proposes a quantization-based image authentication scheme using two-dimensional (2D) barcodes to protect important features. Compared with older linear barcodes, 2D barcodes are a machine-readable representation of binary data that possess capabilities of location and tolerance. This paper presents a method for incorporating VQ-compressed code into 2D barcodes and embedding those barcodes into the image itself. Experimental results showed that VQ codes can be completely reserved during data recovery even though quick response codes sustain certain perceptible distortions. Moreover, the proposed scheme provided higher quality authenticated and recovered images compared with previous methods. <s> BIB016 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> Self-embedding watermarking can be used for image tampering recovery. In this work, the authors proposed a new image self-embedding scheme based on optimal iterative block truncation coding and non-uniform watermark sharing. Experimental results demonstrate that the proposed scheme can achieve better performance of tampering recovery than some of state-of-the-art schemes. <s> BIB017 </s> A recent survey of self-embedding fragile watermarking scheme for image authentication with recovery capability <s> Comparison and discussion <s> This paper proposes a novel tamper detection, localization, and recovery scheme for encrypted images with Discrete Wavelet Transformation (DWT) and Compressive Sensing (CS). The original image is first transformed into DWT domain and divided into important part, that is, low-frequency part, and unimportant part, that is, high-frequency part. For low-frequency part contains the main information of image, traditional chaotic encryption is employed. Then, high-frequency part is encrypted with CS to vacate space for watermark. The scheme takes the processed original image content as watermark, from which the characteristic digest values are generated. Comparing with the existing image authentication algorithms, the proposed scheme can realize not only tamper detection and localization but also tamper recovery. Moreover, tamper recovery is based on block division and the recovery accuracy varies with the contents that are possibly tampered. If either the watermark or low-frequency part is tampered, the recovery accuracy is 100%. The experimental results show that the scheme can not only distinguish the type of tamper and find the tampered blocks but also recover the main information of the original image. With great robustness and security, the scheme can adequately meet the need of secure image transmission under unreliable conditions. <s> BIB018
Comparison of different existing self-embedding fragile watermarking techniques in the spatial domain is presented in Table 2 . Meanwhile, Table 3 shows the comparison of self-embedding fragile watermarking techniques in the frequency domain. Overall, from these tables, it can be observed that most of the fragile watermarking techniques are in a spatial domain, using LSB embedding technique. Based on the previous sections-summarised in Tables 2  and 3 -eight criteria can be categorised to compare each watermarking approach based on the embedding domain. Most of the methods differentiate in two major watermark components: authentication/check bits and recovery bits. For tamper recovery, the watermark generation which is selected using the frequency domain  BIB010 BIB015 has better results than the watermark generation using spatial domains BIB011  BIB005 , i.e. average intensity of blocks. This can be seen from the value of PSNR results after the recovery process. Estimates of fragile watermarking-based techniques are designed into the eight criteria with the following explanation: (1) watermarking approach: this term represents the technique used for image authentication  and recovery using fragile watermarking; (2) watermark generation: this term represents the kind of watermark generation used in each image authentication and recovery scheme; (3) segmented block size: this term indicates the block size (in n × n pixels) of each non-overlapping or overlapping block division in scheme addresses; (4) embedding technique: this term represents the kind of embedding techniques used in each scheme; (5) watermark payload: this term is related to the number of hidden information embedded; (6) PSNR watermarked image: this term represents the visual quality of the watermarked image in each scheme. PSNR larger than 40 dB is considered to be the threshold of a very good visual quality of the reconstructed image. While the PSNR lower than 30 dB would be considered as inadequate image quality. (7) Attacks: this term represents the kind of attacks used in each image authentication and recovery scheme. There are various possible malicious or accidental attacks that may be imposed on the watermark. The availability of a wide range of image processing allows for attacks on watermarking system resilience. From Tables 2 and 3 , most of the attacks include the general tampering (cropping) and the collage attack. (8) PSNR of restored image: this term represents the visual quality of the restored image in each scheme. A comparative explanation of the advantages and disadvantages of each method is as follows. In a paper  , Qin et al. have proposed a self-embedding watermarking scheme that is adaptive to the number of insertion bits, where for more complex blocks they are inserted more bits than the smooth blocks. Besides, this method uses one LSB similar to Zhang BIB002 , thus the watermarked image is better. On the contrary, the ability to restore is reduced and unable to withstand content-based attacks. Similarly, the Sreenivas's method BIB012 proposes a payload watermark for different restorations depending on the level of similarity to the average value for blocks of 2 × 2 pixels. The lack of this method requires a long time because finding similarities with seven conditions and the detection process requires additional methods. Kiatpapan BIB011 has proposed a simple method with dual watermarking. A limitation of the proposed method was that it will not be able to recover image tamper if the tampering takes place globally across the entire original image. Meanwhile, Singh's method BIB013 and Dholes' method BIB010 were used as block-wise mechanisms with different authentication bit generation. Singh has used two level tampered detection procedures, localisation and recovery with the high probability. Dholes' was used in two phases, one with own image and another with watermarked image. The drawback of both approaches is not resistant to common image processing operations such as JPEG compression, contrast enhancement and filtering. The proposed scheme in  uses a hierarchical reference-bits capacity according to the importance of image contents. They can improve the visual quality recovered results, especially for larger tampering rates, but the generation of reference bits which used reference sharing mechanism BIB002 depends on the proportion of different detection results. In addition, for larger tampering rates, the method proposed by Qin  BIB017 BIB014 produces good recovery results using the overlapping block-wise mechanism. The method proposed by BIB007 BIB006 uses the block-mapping operation and adopts parity BIB013   BIB014 . a Original image. b PSNR = 37.15 dB BIB013 . c PSNR = 44.15 dB  . d PSNR = 44.27 dB  . e PSNR = 44.16 BIB014 Rakhmawati check and the intensity-relations check to thwart various malicious attacks. However, unlike He's method BIB005 , it cannot be used on full frames of an image as it would destroy the intelligibility of the content. Li BIB003 has proposed a dual-redundant ring structure and two tamper detection schemes, which improve the quality of the restored image. However, it cannot withstand mild distortions such as random noise and JPEG compression; another disadvantage is the possibility of detection errors because the blocks used are too large, so that if one sub-block is damaged then the entire block will be marked as an error. In method BIB015 , all extracted watermark data contribute to the recovery of content, and the accuracy of the restoration coefficient depends on the amount of available watermark data. Furthermore, the paper BIB004 aims to show that having a known fault location, image damage can be modelled and handled as a deletion error. But reference data can be destroyed by some image processing operations, such as filtering, compressing and additional noise interference, so content recovery is disabled. A different method was proposed recently by Wu BIB016 where an image authentication scheme was proposed to exploit QR codes to protect the integrity of significant VQ authentication data. This method only focuses on the authentication process while the recovery process requires repetition until all blocks undergoing changes are reconstructed. Grouping is different in Table 2 using the frequency domain. Method BIB001 BIB008 BIB016 BIB018 take advantage of robust watermarking for generating recovery bits inserted into the LL sub band on the DWT. The main drawback of this method is that computing is quite high and the watermark insertion capacity is low. In most of the watermarking schemes mentioned above, data that represent the main content in an area are always poured into other areas for content recovery on the recipient's side  . When certain regions containing original information are damaged or lost, however, it is not possible to recover original content in the previous area. In other words, content recovery has failed. For all uses, the fragile watermarking method has a disadvantage where watermarks can be destroyed by image processing operations such as contrast enhancement, JPEG compression, filtering and so on. Therefore, in the future, semi-fragile watermarking methods can be developed that are strong against these attacks and have good storage capabilities BIB009 (Fig. 12 ).