A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> The rapid evolution of digital image manipulation and transmission techniques has created a pressing need for the protection of the intellectual property rights on images. A copyright protection method that is based on hiding an ‘invisible’ signal, known as digital watermark, in the image is presented in this paper. Watermark casting is performed in the spatial domain by slightly modifying the intensity of randomly selected image pixels. Watermark detection does not require the existence of the original image and is carried out by comparing the mean intensity value of the marked pixels against that of the pixels not marked. Statistical hypothesis testing is used for this purpose. Pixel modifications can be done in such a way that the watermark is resistant to JPEG compression and lowpass filtering. This is achieved by minimizing the energy content of the watermark signal at higher frequencies while taking into account properties of the human visual system. A variation that generates image dependent watermarks as well as a method to handle geometrical distortions are presented. An extension to color images is also pursued. Experiments on real images verify the effectiveness of the proposed techniques. <s> BIB001 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Digital image manipulation software is now readily available on personal computers. It is therefore very simple to tamper with any image and make it available to others. Insuring digital image integrity becomes a major issue. In this paper, we propose an original method to protect image authenticity using an invisible and robust watermark. Our scheme is independent of the signer, however the latter must have a high capacity and be able to extract the watermark in full blind detection mode. Our approach is based on the extraction of features from the image. These features are chosen so as to be unaffected by non malicious alterations such as lossy compression. They are embedded in the image using an iterative process so that watermarked image features and information contained in the watermark coincide perfectly. The authenticity is verified by comparing the features of the tested image, with those of the original image recovered from the watermark. (6 pages) <s> BIB002 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> In this paper, we describe a class of attacks on certain block-based oblivious watermarking schemes. We show that oblivious watermarking techniques that embed information into a host image in a block-wise independent fashion are vulnerable to a counterfeiting attack. Specifically, given a watermarked image, one can forge the watermark it contains into another image without knowing the secret key used for watermark insertion and in some cases even without explicitly knowing the watermark. We demonstrate successful implementations of this attack on a few watermarking techniques that have been proposed in the literature. We also describe a possible solution to this problem of block-wise independence that makes our attack computationally intractable. <s> BIB003 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> We describe a watermarking scheme for ownership verification and authentication. Depending on the desire of the user, the watermark can be either visible or invisible. The scheme can detect any modification made to the image and indicate the specific locations that have been modified. If the correct key is specified in the watermark extraction procedure, then an output image is returned showing a proper watermark, indicating the image is authentic and has not been changed since the insertion of the watermark. Any modification would be reflected in a corresponding error in the watermark. If the key is incorrect, or if the image was not watermarked, or if the watermarked image is cropped, the watermark extraction algorithm will return an image that resembles random noise. Since it requires a user key during both the insertion and the extraction procedures, it is not possible for an unauthorized user to insert a new watermark or alter the existing watermark so that the resulting image will pass the test. We present secret key and public key versions of the technique. <s> BIB004 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> A data-hiding technique called the "bipolar multiple-number base" was developed to provide capabilities of authentication, integration, and confidentiality for an electronic patient record (EPR) transmitted among hospitals through the Internet. The proposed technique is capable of hiding those EPR related data such as diagnostic reports, electrocardiogram, and digital signatures from doctors or a hospital into a mark image. The mark image could be the mark of a hospital used to identify the origin of an EPR. Those digital signatures from doctors and a hospital could be applied for the EPR authentication. Thus, different types of medical data can be integrated into the same mark image. The confidentiality is ultimately achieved by decrypting the EPR related data and digital signatures with an exact copy of the original mark image. The experimental results validate the integrity and the invisibility of the hidden EPR related data. This newly developed technique allows all of the hidden data to be separated and restored perfectly by authorized users. <s> BIB005 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Digital watermarking embedding is a hot research field of image processing. Digital watermarking is only possible because our vision system is not perfect. A number of applications have emerged such as copyright notification, time stamp and automated monitoring. There have been ingenious works on watermarking capacity, which all assume the attack distortion are Gaussian additive distribution. We argue that these results are beautiful but not practical. It is hard to classify different attacking methods into a uniform format (especially as Gaussian distribution). In the other hand, the capacity of a given image's information is an interesting and important topic. Instead of conventional analysis based on non-precise assumption of attack distortion, this paper concentrates on the problem of how much information that image can carry without much visibility distortion. Our work is based on wavelet transform and mean-squared error since we believe they are representative measure for most work. Comparing with the former work on the watermarking capacity, this paper pays more attention to the influence on capacity of widely used technique such as spread spectrum. In the last part of this paper, we discuss future trends of new watermarking algorithm and their influence on capacity. <s> BIB006 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Protection of digital multimedia content has become an increasingly important issue for content owners and service providers. As watermarking is identified as a major technology to achieve copyright protection, the relevant literature includes several distinct approaches for embedding data into a multimedia element (primarily images, audio, and video). Because of its growing popularity, the Discrete Wavelet Transform (DWT) is commonly used in recent watermarking schemes. In a DWT-based scheme, the DWT coefficients are modified with the data that represents the watermark. In this paper, we present a hybrid scheme based on DWT and Singular Value Decomposition (SVD). After decomposing the cover image into four bands, we apply the SVD to each band, and embed the same watermark data by modifying the singular values. Modification in all frequencies allows the development of a watermarking scheme that is robust to a wide range of attacks. <s> BIB007 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Abstract Medical images are currently created digitally and stored in the radiology department’s picture archiving and communication system. Reports are usually stored in the electronic patient record of other information systems, such as the radiology information system (RIS) and the hospital information system (HIS). But high-quality services can only be provided if electronic patient record data is integrated with digital images in picture archiving and communication systems. Clinicians should be able to access both systems’ data in an integrated and consistent way as part of their regular working environment, whether HIS or RIS. Also, this system should allow for teleconferencing with other users, eg, for consultation with a specialist in the radiology department. This article describes a web-based solution that integrates the digital images of picture archiving and communication systems with electronic patient record/HIS/RIS data and has built-in teleconferencing functionality. This integration has been successfully tested using three different commercial RIS and HIS products. <s> BIB008 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> A ROI (region of interest) of a medical image is an area including important information and must be stored without any distortion. In order to achieve optimal compression as well as satisfactory visualization of medical images, we compress the ROI by lossless compression, and the rest by lossy compression. Furthermore, security is an important issue in web-based medical information system. Watermarking skill is often used for protecting medical images. In this paper, we present a robust technique embedding the watermark of signature information or textual data around the ROI of a medical image based on genetic algorithms. A fragile watermark is adopted to detect any unauthorized modification. The embedding of watermark in the frequency domain is more difficult to be pirated than in spatial domain. <s> BIB009 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> In this paper, a robust watermark scheme for copyright protection is proposed. By modifying the original image in transform domain and embedding a watermark in the difference values between the original image and its reference image, the proposed scheme overcomes the weak robustness problem of embedding a watermark in the spatial domain. Besides, the watermark extraction does not require the original image so it is more practical in real application. The experimental results show that the proposed scheme provides not only good image quality, but is also robust against various attacks, such as JPEG lossy compression, filtering and noise addition. <s> BIB010 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> This paper presents a content-based digital image-watermarking scheme, which is robust against a variety of common image-processing attacks and geometric distortions. The image content is represented by important feature points obtained by our image-texture-based adaptive Harris corner detector. These important feature points are geometrically significant and therefore are capable of determining the possible geometric attacks with the aid of the Delaunay-tessellation-based triangle matching method. The watermark is encoded by both the error correcting codes and the spread spectrum technique to improve the detection accuracy and ensure a large measure of security against unintentional or intentional attacks. An image-content-based adaptive embedding scheme is applied in discrete Fourier transform (DFT) domain of each perceptually high textured subimage to ensure better visual quality and more robustness. The watermark detection decision is based on the number of matched bits between the recovered and embedded watermarks in embedding subimages. The experimental results demonstrate the robustness of the proposed method against any combination of the geometric distortions and various common image-processing operations such as JPEG compression, filtering, enhancement, and quantization. Our proposed system also yields a better performance as compared with some peer systems in the literature. <s> BIB011 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> This work proposes a method of embedding digital watermarks into audio signals in the time domain. The proposed algorithm exploits differential average-of-absolute-amplitude relations within each group of audio samples to represent one-bit information. The principle of low-frequency amplitude modification is employed to scale amplitudes in a group manner (unlike the sample-by-sample manner as used in pseudonoise or spread-spectrum techniques) in selected sections of samples so that the time-domain waveform envelope can be almost preserved. Besides, when the frequency-domain characteristics of the watermark signal are controlled by applying absolute hearing thresholds in the psychoacoustic model, the distortion associated with watermarking is hardly perceivable by human ears. The watermark can be blindly extracted without knowledge of the original signal. Subjective and objective tests reveal that the proposed watermarking scheme maintains high audio quality and is simultaneously highly robust to pirate attacks, including MP3 compression, low-pass filtering, amplitude scaling, time scaling, digital-to-analog/analog-to-digital reacquisition, cropping, sampling rate change, and bit resolution transformation. Security of embedded watermarks is enhanced by adopting unequal section lengths determined by a secret key. <s> BIB012 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> This paper discussed security of medical images and reviewed some work done regarding them. A fragile watermarking scheme was then proposed that could detect tamper and subsequently recover the image. Our scheme required a secret key and a public chaotic mixing algorithm to embed and recover a tampered image. The scheme was also resilient to VQ attack. The purposes were to verify the integrity and authenticity of medical images. We used 800x600x8 bits ultrasound (US) greyscale images in our experiment. We tested our algorithm for up to 50% tampered block and obtained 100% recovery for spread-tampered block. I. INTRODUCTION Security of medical images, derived from strict ethics and legislative rules, gives rights to the patient and duties to the health professionals. This imposes three mandatory characteristics: confidentiality, reliability and availability: • Confidentiality means that only the entitled persons have access to the images; • Reliability which has two aspects; Integrity: the image has not been modified by non-authorized person, and authentication: a proof that the image belongs indeed to the correct patient and is issued from the correct source; <s> BIB013 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> In this paper, we propose a blind image watermarking algorithm based on the multiband wavelet transformation and the empirical mode decomposition. Unlike the watermark algorithms based on the traditional two-band wavelet transform, where the watermark bits are embedded directly on the wavelet coefficients, in the proposed scheme, we embed the watermark bits in the mean trend of some middle-frequency subimages in the wavelet domain. We further select appropriate dilation factor and filters in the multiband wavelet transform to achieve better performance in terms of perceptually invisibility and the robustness of the watermark. The experimental results show that the proposed blind watermarking scheme is robust against JPEG compression, Gaussian noise, salt and pepper noise, median filtering, and Con-vFilter attacks. The comparison analysis demonstrate that our scheme has better performance than the watermarking schemes reported recently. <s> BIB014 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Digital medical images are very easy to be modified for illegal purposes. For example, microcalcification in mammography is an important diagnostic clue, and it can be wiped off intentionally for insurance purposes or added intentionally into a normal mammography. In this paper, we proposed two methods to tamper detection and recovery for a medical image. A 1024 × 1024 x-ray mammogram was chosen to test the ability of tamper detection and recovery. At first, a medical image is divided into several blocks. For each block, an adaptive robust digital watermarking method combined with the modulo operation is used to hide both the authentication message and the recovery information. In the first method, each block is embedded with the authentication message and the recovery information of other blocks. Because the recovered block is too small and excessively compressed, the concept of region of interest (ROI) is introduced into the second method. If there are no tampered blocks, the original image can be obtained with only the stego image. When the ROI, such as microcalcification in mammography, is tampered with, an approximate image will be obtained from other blocks. From the experimental results, the proposed near-lossless method is proven to effectively detect a tampered medical image and recover the original ROI image. In this study, an adaptive robust digital watermarking method combined with the operation of modulo 256 was chosen to achieve information hiding and image authentication. With the proposal method, any random changes on the stego image will be detected in high probability. <s> BIB015 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Digital watermarking, one of the data hiding techniques has become an emerging area of research due to the wide spread use of Internet and intranets. Though the watermark is used for authentication purpose, its methodology has been adapted for hiding data in many applications namely electronic patient record (EPR) data hiding in medical images. Medical images are usually large sized images and stored without loss of redundancy. Recent researches have proven that appropriate level of JPEG (joint picture expert group) compression may be used on these image types without loss of diagnostic content. This has provided an opportunity for more rapid image transmission. This work focuses on the estimation of the data hiding capacity of region of interest (ROI) medical images and optimizing the JPEG survival level that allow acceptable JPEG compression for conventional spatial domain watermarking techniques namely LSB technique, additive technique and spread spectrum technique <s> BIB016 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> This paper presents a lossless watermarking scheme in the sense that the original image can be exactly recovered from the watermarked one, with the purpose of verifying the integrity and authenticity of medical images. In addition, the scheme has the capability of not introducing any embedding-induced distortion in the region of interest (ROI) of a medical image. Difference expansion of adjacent pixel values is employed to embed several bits. A region of embedding, which is represented by a polygon, is chosen intentionally to prevent introducing embedding distortion in the ROI. Only the vertex information of a polygon is transmitted to the decoder for reconstructing the embedding region, which improves the embedding capacity considerably. The digital signature of the whole image is embedded for verifying the integrity of the image. An identifier presented in electronic patient record (EPR) is embedded for verifying the authenticity by simultaneously processing the watermarked image and the EPR. Combining with fingerprint system, patient’s fingerprint information is embedded into several image slices and then extracted for verifying the authenticity. <s> BIB017 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Digital audio, video, images, and documents are flying through cyberspace to their respective owners. Unfortunately, along the way, individuals may choose to intervene and take this content for themselves. Digital watermarking and steganography technology greatly reduces the instances of this by limiting or eliminating the ability of third parties to decipher the content that he has taken. The many techiniques of digital watermarking (embedding a code) and steganography (hiding information) continue to evolve as applications that necessitate them do the same. The authors of this second edition provide an update on the framework for applying these techniques that they provided researchers and professionals in the first well-received edition. Steganography and steganalysis (the art of detecting hidden information) have been added to a robust treatment of digital watermarking, as many in each field research and deal with the other. New material includes watermarking with side information, QIM, and dirty-paper codes. The revision and inclusion of new material by these influential authors has created a must-own book for anyone in this profession. ::: ::: *This new edition now contains essential information on steganalysis and steganography ::: *New concepts and new applications including QIM introduced ::: *Digital watermark embedding is given a complete update with new processes and applications <s> BIB018 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Publisher Summary ::: This chapter provides the conceptual models of watermarking. These models serve as ways of thinking about actual watermarking systems. They fall into two broad groups: models based on a view of watermarking as a method of communication and models based on geometric views of watermarking algorithms. It describes three models of watermarking systems based on the traditional model of a communications channel. These differ in how the cover Work is incorporated into the system. In the basic model, the cover Work is considered noise added during transmission of the watermark signal and in models of watermarking as communications with side information at the transmitter, the cover Work is still considered noise, but the watermark encoding process is provided with its value as side information. In models of watermarking as multiplexing, the cover Work and the watermark are considered two messages multiplexed together for reception by two different “receivers”: a human and a watermark detector, respectively. Part of a watermarking system can be viewed as an extraction process that projects or distorts media space into a marking space. The rest can then be viewed as a simpler watermarking system that operates in marking space rather than in media space. Many watermarking systems fall into the class of correlation-based systems, in which the detector uses some form of correlation as a detection metric. This is true even of many systems not explicitly described as using correlation-based detection. <s> BIB019 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> The development of effective image authentication techniques is of remarkably growing interest. Some recently developed fragile, semi-fragile/robust or hybrid-watermarking algorithms not only verify the authenticity of the watermarked image but also provide self reconstruction capabilities. However, several algorithms have been reported as vulnerable to various attacks, especially blind pattern matching attacks, with insufficient security. We propose a new blind dual-domain self-embedding watermarking scheme with more secure embedding processes of the image's blocks fragile signatures and robust approximations and more reliable local alterations detection with auto-correction capabilities, surviving normal image content preserving operations. Hence it prevents falsification, the real threat to authentication. <s> BIB020 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> An effective dual watermark scheme for image tamper detection and recovery is proposed in this paper. In our algorithm, each block in the image contains watermark of other two blocks. That is to say, there are two copies of watermark for each non-overlapping block in the image. Therefore, we maintain two copies of watermark of the whole image and provide second chance for block recovery in case one copy is destroyed. A secret key, which is transmitted along with the watermarked image, and a public chaotic mixing algorithm are used to extract the watermark for tamper recovery. By using our algorithm, a 90% tampered image can be recovered to a dim yet still recognizable condition (PSNR ~20dB). Experimental results demonstrate that our algorithm is superior to the compared techniques, especially when the tampered area is large. <s> BIB021 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Protection against geometric distortions and common image processing operations with blind detection becomes a much challenging task in image watermarking. To achieve this, in this paper we propose a content-based watermarking scheme that combines the invariant feature extraction with watermark embedding by using Tchebichef moments. Harris-Laplace detector is first adopted to extract feature points, and then non-overlapped disks centered at feature points are generated. These disks are invariant to scaling and translation distortions. For each disk, orientation alignment is then performed to achieve rotation invariant. Finally, the watermark is embedded in magnitudes of Tchebichef moments of each disk via dither modulation to realize the robustness to common image processing operations and the blind detection. Thorough simulation results obtained by using the standard benchmark, Stirmark, demonstrate that the proposed method is robust against various geometric distortions as well as common image processing operations and outperforms representative image watermarking schemes. <s> BIB022 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Medical image is usually comprised of region of interest (ROI) and region of non interest (RONI). ROI is the region that contains the important information from diagnosis point of view so it must be stored without any distortion. We have proposed a digital watermarking technique which avoids the distortion of image in ROI by embedding the watermark information in RONI. The watermark is comprised of patient information, hospital logo and message authentication code, computed using hash function. Earlier BCH encryption of watermark is performed to ensure inaccessibility of embedded data to the adversaries. <s> BIB023 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> In this article, we propose a new additive lossless watermarking scheme which identifies parts of the image that can be reversibly watermarked and conducts message embedding in the conventional Haar wavelet transform coefficients. Our approach makes use of an approximation of the image signal that is invariant to the watermark addition for classifying the image in order to avoid over/underflows. The method has been tested on different sets of medical images and some usual natural test images as Lena. Experimental result analysis conducted with respect to several aspects including data hiding capacity and image quality preservation, shows that our method is one of the most competitive existing lossless watermarking schemes in terms of high capacity and low distortion. <s> BIB024 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> In this article, a new fragile, blind, high payload capacity, ROI (Region of Interest) preserving Medical image watermarking (MIW) technique in the spatial domain for gray scale medical images is proposed. We present a watermarking scheme that combines lossless data compression and encryption technique in application to medical images. The effectiveness of the proposed scheme, proven through experiments on various medical images through various image quality measure matrices such as PSNR, MSE and MSSIM enables us to argue that, the method will help to maintain Electronic Patient Report(EPR)/DICOM data privacy and medical image integrity. <s> BIB025 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Teleradiology applications and universal availability of patient records using web-based technology are rapidly gaining importance. Consequently, digital medical image security has become an important issue when images and their pertinent patient information are transmitted across public networks, such as the Internet. Health mandates such as the Health Insurance Portability and Accountability Act require healthcare providers to adhere to security measures in order to protect sensitive patient information. This paper presents a fully reversible, dual-layer watermarking scheme with tamper detection capability for medical images. The scheme utilizes concepts of public-key cryptography and reversible data-hiding technique. The scheme was tested using medical images in DICOM format. The results show that the scheme is able to ensure image authenticity and integrity, and to locate tampered regions in the images. <s> BIB026 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> This paper presents a key based generic model for digital image watermarking. The model aims at addressing an identified gap in the literature by providing a basis for assessing different watermarking requirements in various digital image applications. We start with a formulation of a basic watermarking system, and define system inputs and outputs. We then proceed to incorporate the use of keys in the design of various system components. Using the model, we also define a few fundamental design and evaluation parameters. To demonstrate the significance of the proposed model, we provide an example of how it can be applied to formally define common attacks. <s> BIB027 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> We propose a robust quantization-based image watermarking scheme, called the gradient direction watermarking (GDWM), based on the uniform quantization of the direction of gradient vectors. In GDWM, the watermark bits are embedded by quantizing the angles of significant gradient vectors at multiple wavelet scales. The proposed scheme has the following advantages: 1) increased invisibility of the embedded watermark because the watermark is embedded in significant gradient vectors, 2) robustness to amplitude scaling attacks because the watermark is embedded in the angles of the gradient vectors, and 3) increased watermarking capacity as the scheme uses multiple-scale embedding. The gradient vector at a pixel is expressed in terms of the discrete wavelet transform (DWT) coefficients. To quantize the gradient direction, the DWT coefficients are modified based on the derived relationship between the changes in the coefficients and the change in the gradient direction. Experimental results show that the proposed GDWM outperforms other watermarking methods and is robust to a wide range of attacks, e.g., Gaussian filtering, amplitude scaling, median filtering, sharpening, JPEG compression, Gaussian noise, salt & pepper noise, and scaling. <s> BIB028 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Medical applications such as telediagnosis require information exchange over insecure networks. Therefore, protection of the integrity and confidentiality of the medical images is an important issue. Another issue is to store electronic patient record (EPR) in the medical image by steganographic or watermarking techniques. Studies reported in the literature deal with some of these issues but not all of them are satisfied in a single method. A medical image is distributed among a number of clinicians in telediagnosis and each one of them has all the information about the patient's medical condition. However, disclosing all the information about an important patient's medical condition to each of the clinicians is a security issue. This paper proposes a (k, n) secret sharing scheme which shares medical images among a health team of n clinicians such that at least k of them must gather to reveal the medical image to diagnose. Shamir's secret sharing scheme is used to address all of these security issues in one method. The proposed method can store longer EPR strings along with better authenticity and confidentiality properties while satisfying all the requirements as shown in the results. <s> BIB029 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> Since the difference expansion (DE) technique was proposed, many researchers tried to, improve its performance in terms of hiding capacity and visual quality. In this paper, a new scheme, based on DE is proposed in order to increase the hiding capacity for medical images. One of the characteristics of medical images, among the other types of images, is the large smooth regions. Taking advantage of this characteristic, our scheme divides the image into two regions; smooth region and non-smooth region. For the smooth region, a high embedding capacity scheme is applied, while the original DE method is applied to the non-smooth region. Sixteen DICOM images of different modalities were used for testing the proposed schemes. The results showed that the proposed scheme has higher hiding capacity compared to the original schemes. <s> BIB030 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Choice of Design and Evaluation Parameters <s> In most of the digital image watermarking schemes, it becomes a common practice to address security in terms of robustness, which is basically a norm in cryptography. Such consideration in developing and evaluation of a watermarking scheme may severely affect the performance and render the scheme ultimately unusable. This paper provides an explicit theoretical analysis towards watermarking security and robustness in figuring out the exact problem status from the literature. With the necessary hypotheses and analyses from technical perspective, we demonstrate the fundamental realization of the problem. Finally, some necessary recommendations are made for complete assessment of watermarking security and robustness. <s> BIB031
Watermarking requirements for medical images are mainly defined in terms of security and privacy, fidelity, and computational properties. Hence, security and privacy requirements characterize a watermarking scheme to achieve data hiding, integrity control, and authenticity objectives as discussed in previous section. Fidelity requirements guarantee that the watermarked medical images are useable for diagnosis and other clinical uses. Besides, the computational properties help obtain the cost benefit and feasibility analysis for practical implementation. All these watermarking requirements, on the other hand, define various watermarking design and evaluation parameters in an application scenario. Design parameters help characterize the development of a watermarking scheme, whereas the evaluation parameters help determine the performance of a developing/existing scheme. Typical parameters for watermark generation and embedding include visibility, blindness, embedding capacity, imperceptibility/perceptual similarity, etc. Similarly, blindness, invertibility, robustness, error probability, etc., are the parameters for the detection BIB027 . Moreover, deploying a watermarking system in medical image applications broadly includes two phases, namely a development phase and a validation phase as illustrated in Fig. 3 . In the development phase, optimum criteria for the necessary design parameters of the system are to be defined properly according to the medical image requirements, since all the design parameters of watermarking frequently influence one another (directly or indirectly) BIB019 . Similarly, it is also necessary to have a careful consideration on the evaluation parameters, their suitable measures, and the requirements of the medical images in the validation phase, in order to justify the suitability of existing/developing watermarking schemes for medical image application. The system design and evaluation parameters for image watermarking are mainly associated with its core components: watermark generation, embedding, and detection BIB027 . Various design and evaluation parameters play an important role in achieving a particular objective in an application scenario, which has been reviewed for teleradiology application and is discussed in the following. Visibility Visible watermarking are important in recognition and support of possessing a digital image, where watermarking objectives is mainly to show some necessary information such as logo, icon, courtesy, etc., through the watermarked image. Contrariwise, invisible watermarks are used in digital image applications, where watermarking objectives are to addressing security issues of the images. Like various digital image applications BIB022 BIB007 BIB010 BIB001 BIB024 BIB011 BIB002  BIB004 , invisibility of the watermark appears to be the main interest in the research of medical imaging [8-10, 12, 13, 41, 77-79] . Robustness Robustness is an important parameter for the watermarking detector defined in different ways BIB031 . Robustness, basically, is defined as the degree of resistance of a watermarking scheme to modifications of the host signal due to either common signal processing, or operations devised specifically in order to render the watermark undetectable  . This parameter categorizes watermarking schemes to be robust, fragile, and semi-fragile. In a robust watermarking, a watermark usually carries information regarding the owner in order to validate who the image belongs to (e.g., which person, which institute or organization, etc.). Thus, these watermarking schemes are being used for content authentication purposes in various digital image applications (e.g., copyright protection) BIB022 BIB011 BIB009 BIB028 BIB012  BIB014  . Semi-fragile and fragile watermarks are being used to carry much information about itself, its owner's metadata, its distribution, etc., and are thus used for annotation (e.g., hiding ETR or EPR, etc.) BIB025 BIB005 BIB029 BIB008   and integrity control (e.g., tamper detection and recovery) BIB026 BIB015 BIB020 BIB021 BIB013 . Blindness Blindness in watermarking refers to the ability of a component function (e.g., watermark generation, detection) to work without any original version of input (e.g., image or watermark, etc.). Non-blindness in watermark generation is important while an original image dependent watermark is required. An original imagedependent watermark is helpful in addressing ambiguity and forgery attacks (e.g., copy attacks) BIB019 . Here, if the watermark is not dependent on the original image, it can be easily copied to another image or forged to output an invalid watermarked image BIB003 . Besides, blindness in detection is important, where availability of the original image or watermark at the detector can thwart watermarking objectives. Non-blindness in detection is used sometimes in developing tamper-recovery watermarking schemes, where the recovery of tampered regions is often difficult to achieve from the watermarked image itself. Embedding Capacity Embedding capacity is generally measured by number of embedding bits. High embedding capacity is a key issue in developing annotation or integrity control watermarking schemes BIB030 , which are generally of fragile or semi-fragile nature to some common image processing. Achieving high embedding capacity often introduces more distortions to a watermarked image and thereby often makes it difficult to preserve high imperceptibility. A robust watermarking used for content authentication purpose requires comparatively lower embedding capacity than that required for annotations purposes of a fragile/semifragile watermark  BIB006 . Research shows that LSB embedding techniques offer comparatively higher embedding capacity BIB023 BIB016 . Invertibility Invertibility of a watermarking system indicates the detection function to be the inverse of the embedding function. Invertible (or sometimes referred to as reversible or lossless) watermarking is of special interest in digital image applications where no distortions are allowed in the original image. Therefore, an original image is required to be restored from respective watermarked images by the detector. Invertibility seldom gets interest for nonblind detector since detection itself requires the original image, although developing a blind detector for invertible watermarking is more challenging, especially when a high embedding capacity is desired. Developing this type of watermarking received much attention in medical image applications to avoid any misdiagnosis from distortions in a watermarked image BIB026 BIB024 BIB017 . Perceptual Similarity Perceptual similarity determines the degree of imperceptibility between the original image and its watermarked version, especially in developing an invisible watermarking scheme BIB019 . Different similarity metrics are used for this parameter such as correlation quality; signal-to-noise ratio (SNR), peak SNR (PSNR), weighted Fig. 3 Interlinking of digital watermarking with medical image applications PSNR, mean square error; structural similarity (SSIM), mean SSIM; and normalized cross-correlation (NCC). In medical image watermarking applications, perceptual similarity must be very high to avoid any risk of misdiagnosis. Security Security requirements of watermarking include the legitimate access, use, disclosure, disruption, modification, or perusal of the watermarking system. Determining these security requirements in a target application is crucial for the system design, and that can be determined through comprehensive risk management (e.g., examining security policy, access control, physical and environmental security, operation managements, etc.)  97] . Error Probability Error probability is another important parameter for assessing detection performance of a watermarking scheme. Irrespective of application scenarios, zero error probability is always desirable, although achieving this is practically difficult considering higher degrees of robustness to any distortions BIB018 . However, like in other digital image applications, keeping the error probabilities lower as much as possible is very important in a medical image application scenario in order to ensure reliable detection. Some of the important and commonly used error probability metrics are bit error rate, false-positive rate, false-negative rate, etc.