A Review of Medical Image Watermarking Requirements for Teleradiology <s> Limitations of the Existing Security Measures <s> Because of the importance of the security issues in the management of medical information, we suggest the use of watermarking techniques to complete the existing measures for protecting medical images. We discuss the necessary requirements for such a system to be accepted by medical staff and its complementary role with respect with existing security systems. We present different scenarios, one devoted to the authentication and tracing of the images, the second to the integrity control of the patient's record. <s> BIB001 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Limitations of the Existing Security Measures <s> Purpose: Data security becomes an important issue in telemedicine when medical information is transmitted over wide area network. Generally, security is characterized in terms of privacy, authenticity and integrity of digital data. We present a method here which can meet the requirements of privacy, authenticity, and integrity for archiving and transmitting of sectional image such as CT, MR. Methods: The method is described as follows: firstly, image segmentation was done and some patient information was read from image DICOM header. Second, a digital signature for the segmented image was produced using the image sender's private key. Afterwards, the digital signature and patient information were concatenated and embedded into the background area of the image. Finally, the whole image was encrypted to form a digital envelope using the receiver's public key. Results: (1) The image can only be decrypted and read by authorized user who own the private key of the receiving site. (2) The authenticity and integrity can be tested by signature verification. Conclusions: The preliminary results demonstrate that the method we presented here is an effective method for secure archiving and transmitting for sectional medical images. <s> BIB002 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Limitations of the Existing Security Measures <s> The control of the integrity and authentication of medical images is becoming ever more important within the Medical Information Systems (MIS). The intra- and interhospital exchange of images, such as in the PACS (Picture Archiving and Communication Systems), and the ease of copying, manipulation and distribution of images have brought forth the security aspects. In this paper we focus on the role of watermarking for MIS security and address the problem of integrity control of medical images. We discuss alternative schemes to extract verification signatures and compare their tamper detection performance. <s> BIB003 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Limitations of the Existing Security Measures <s> Medical image security is an important issue when digital images and their pertinent patient information are transmitted across public networks. Mandates for ensuring health data security have been issued by the federal government such as Health Insurance Portability and Accountability Act (HIPAA), where healthcare institutions are obliged to take appropriate measures to ensure that patient information is only provided to people who have a professional need. Guidelines, such as digital imaging and communication in medicine (DICOM) standards that deal with security issues, continue to be published by organizing bodies in healthcare. However, there are many differences in implementation especially for an integrated system like picture archiving and communication system (PACS), and the infrastructure to deploy these security standards is often lacking. Over the past 6 years, members in the Image Processing and Informatics Laboratory, Childrens Hospital, Los Angeles/University of Southern California, have actively researched image security issues related to PACS and teleradiology. The paper summarizes our previous work and presents an approach to further research on the digital envelope (DE) concept that provides image integrity and security assurance in addition to conventional network security protection. The DE, including the digital signature (DS) of the image as well as encrypted patient information from the DICOM image header, can be embedded in the background area of the image as an invisible permanent watermark. The paper outlines the systematic development, evaluation and deployment of the DE method in a PACS environment. We have also proposed a dedicated PACS security server that will act as an image authority to check and certify the image origin and integrity upon request by a user, and meanwhile act also as a secure DICOM gateway to the outside connections and a PACS operation monitor for HIPAA supporting information. <s> BIB004 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Limitations of the Existing Security Measures <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> BIB005 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Limitations of the Existing Security Measures <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> BIB006 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Limitations of the Existing Security Measures <s> In this paper, we consider some basic concepts behind the design of existing robust perceptual hashing techniques for content identification. We show the limits of robust hashing from the communication perspectives as well as propose an approach that is able to overcome these shortcomings in certain setups. The consideration is based on both achievable rate and probability of error. We use the fact that most robust hashing algorithms are based on dimensionality reduction using random projections and quantization. Therefore, we demonstrate the corresponding achievable rate and probability of error based on random projections and compare with the results for the direct domain. The effect of dimensionality reduction is studied and the corresponding approximations are provided based on the Johnson-Lindenstrauss lemma. Side-information assisted robust perceptual hashing is proposed as a solution to the above shortcomings. <s> BIB007 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Limitations of the Existing Security Measures <s> Secure authentication of digital medical image content provides great value to the e-Health community and medical insurance industries. Fragile Watermarking has been proposed to provide the mechanism to authenticate digital medical image securely. Transform Domain based Watermarking are typically slower than spatial domain watermarking owing to the overhead in calculation of coefficients. In this paper, we propose a new Discrete Pascal Transform based watermarking technique. Preliminary experiment result shows authentication capability. Possible improvements on the proposed scheme are also presented before conclusions. <s> BIB008 </s> A Review of Medical Image Watermarking Requirements for Teleradiology <s> Limitations of the Existing Security Measures <s> Basic Security Concepts - Why is Computer and Network Security Important. Background and History. The Security Trinity. Information Security. Risk Assessment. Security Models. Basic Terminology. More Basic Terminology. Threats, Vulnerabilities and Attacks - Protocols. The OSI Reference Model. TCP/IP Protocol Suite. Useful Web Sites. Search Engines. Mailing Lists. Encryption, Digital Signatures and Certification - Cryptography. Stream Ciphers. Breaking Ciphers. Block Ciphers. Encryption. Public Key Cryptosystems. Message Integrity. Authentication. Digital Signatures. Competing Standards. Digital Certificates. Limitations of Digital Certificates. Certificate Authorities. Public Key Infrastructure. The Future. The Limitations of Encryption. Kerberos - How Kerberos Works. Kerberos- Limitations. Encryption on the WWW - The World Wide Web. Secure Sockets Layer (HTTPS). Secure HTTP (SHTTP). Microsoft's Internet Explorer. Viewing Digital Certificates with Internet Explorer. Viewing the Encryption Strength of IE5. Viewing Certification Authorities with IE5. Netscape Navigator. Viewing Digital Certificates with Navigator. Authenticode Certificates. E-Mail - E-Mail Issues. E-Mail Issues. Secure E-Mail Protocols. Web-Based E-Mail Services. Security of Stored Messages. Identity: Spoofing and Hiding. E-Mail as a weapon. E-Mail Policies. E-Mail Privacy. Auto-Responses. Operating System Security -- Passwords. Password Attacks. Onetime Passwords. Access Control. Data Redundancy. General Recommendations. Modems. Useful Tools. LAN Security - LAN Guidelines. Controlling End-User Access. Concurrent Logins. Available Disk Space. Restrictions to Location or Workstation. Time/Day Restrictions. Access to Directories and Trustee Rights. File Attributes. Other Privileges. Single Sign-On. Policy-Based Network Management. Honeypot Systems. Network Segmentation. Static IP Addresses vs. DHCP. Media and Protocols - Network Media. Plenum Cabling and Risers. WANs. Redundancy and Alternative Connections. Routers and SNMP - Router Issues. SNMP. Virtual Private Networks - Encryption on the Network. Node-to-Node Encryption. End-to-End Encryption. Where to Encrypt. Virtual Private Networks. PPTP. L2TP. IPSec. SOCKS. Firewalls - Firewalls Pros and Cons. Types of Firewalls. Packet Filters vs. Proxies. Firewall Configurations. Restricting Users' Access to the Internet. Firewall Products. Personal Firewalls. Biometrics - Identification and Authentication. Biometric Identification and Authentication. Biometric Identification Reliability. Backup Authentication. Environmental Conditions. User Acceptance. Security of the Biometric System. Interoperability. Costs vs. Savings. Policies and Procedures - Policies vs. Procedures. Information Security Policy Objectives. Developing Security Policies. Policy and Procedure Manuals. Policy Awareness & Education. Policy Enforcement. Policy Format. Security Policy Suggestions. Information Protection Team. Crisis Management Planning. Sources for Information Policies. Auditing and Intrusion Detection - What is an Audit. Operational Security Audits. System Security Auditing. Activity and Usage Auditing. Audit Mistakes. Deficiencies of Traditional Audit Techniques. Intrusion Detection. Intrusion Detection Systems. Host-Based Intrusion Detection Systems. Network-Based Intrusion Detection Systems. Knowledge-Based Intrusion Detection Systems. Statistical-Based Intrusion Detection Systems. Defense In-Depth Approach . Future Directions. Crisis Management Planning - Crisis Management. Disaster Recovery Planning. Computer Security Incident Response Plan. Browser Security - Cookie Files. Cache Files. Autocomplete. <s> BIB009
Various existing security measures, as illustrated in Table 1 , are being used to protect the medical images and information, and their communications. For example, virtual private network (VPN), firewall, etc., as well as encryption, cryptographic hash function, or their derivatives such as digital signature (DS), machine authentication code (MAC), manipulation detection code (MDC), and perceptual hashing, etc. However, these conventional security measures are considered to have limitations specially in protecting the medical images BIB004 BIB001 BIB006 BIB003    BIB002  , which are summarized in Table 2 and should be properly addressed for the improved security. Firewall and VPN Among various network security measures, firewalls and VPN are common. Along with intrusion detection systems, antivirus systems, etc., those measures are implemented mainly for protecting the information through securing the communications of a system. A firewall is usually placed between two networks to act as a gateway, which is a combination of hardware and software that protects the company's network and computers from possible intrusion by hackers from the external network BIB009 . Canavan BIB009 described this as a fundamental component of any perimeter defence that can have the following uses: (1) keeping unwanted and unauthorized traffic from passing (in or out); (2) providing an efficient Internet access to internal users; (3) monitoring for and notifying of intrusions and network problems; (4) maintaining logs of all communication activities between two networks effectively, which can be used to identify abnormal events. Canavan also described three principal requirements of an effective firewall: (1) it must act as a door through which all traffic must pass (incoming and outgoing); (2) it must allow only authorized traffic to pass; and (3) it must be immune to penetration or compromise. However, a firewall by itself does not assure a secure network, and it represents a single point of failure BIB009 . Firewall, as only a tool, needs proper configuration and regular monitoring. Firewalls that are not properly configured may allow unauthorized users through. In addition, a denial-of-service attack that effectively shuts down the firewall shuts down the network connection to the outside world BIB009 . Moreover, a firewall takes time more or less to examine incoming and outgoing traffic, which tends to degrade network performance. As another significant limitation, firewalls are of no use to track activities on the internal network. While a firewall does make it somewhat more difficult for someone from the outside to get in, the majority of attacks on corporate systems come from the inside, not from the outside BIB009 . In addition to the threat from inside of an organization, firewalls can be circumvented by outsiders BIB009 . As a result, critical systems should be configured to monitor logins, failed logins, and all network activity of the internal systems. A VPN, on the other hand, is a means of transporting traffic in a secure manner over an unsecured network which is achieved by employing some combination of encryption, authentication, and tunnelling  . "Tunnelling" refers to the process of encapsulating or embedding one network protocol to be carried within the packets of a second network. There are several different implementations of VPN protocols such as point-to-point tunnelling protocol (PPTP), Internet protocol security (IPSec), secure sockets layer (SSL), secure shell (SSH), etc. Those protocols have different pros and cons from different technical perspective  . For example, SSL supports transmission control protocol traffic only; SSL and SSH depend on client port forwarding; some protocols use symmetric or weak encryption (e.g., PPTP), and IPSec supports unicast traffic only, etc. However, considering the general perspective of information security, further to firewalls, a VPN can be used to protect the information up to the point of the communication networks. Encryption In order to protect the privacy and confidentiality of electronic health information, encryption has been a commonly accepted technology in health care sector [37] . In cryptography, encryption is the process of transforming information (referred to as plaintext) using an algorithm (called cipher) to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key [38] . The result of the process is encrypted information (called ciphertext). There are two types of encryption: symmetric (private/secret key) encryption (e.g., data encryption standard, Rivest Cipher #4-RC4) and asymmetric (public key) encryption (e.g., Diffie Hellman, digital signature algorithm (DSA)). The strength of the symmetric scheme is largely dependent on the size of the key and on keeping it secret. Generally, the larger the key, the more secure the scheme  . Furthermore, symmetric encryption is relatively fast and widely understood. However, the main weakness of this type of encryption is that the key or algorithm has to be shared  . In addition, symmetric key provides no process for authentication or nonrepudiation  . Here, nonrepudiation is the ability to prevent individuals or entities from denying that a message was sent or received or that file was accessed or altered, when in fact it was. That is why symmetric cryptosystems are not well suited for spontaneous communication over open and unsecured networks  . On the other hand, asymmetric encryption uses two keys as opposed to one key in a symmetric system  . One of them is kept secret and called private key, while the other is made public and called public key. A message is encrypted with the private key and decrypted with the public key. The advantages of this type of encryption include no secret sharing and providing a means of authentication and nonrepudiation with the help of digital certificates. Unlike symmetric cryptosystem, public key allows for secure spontaneous communication over an open network. Besides, it is more scalable for very large systems than symmetric cryptosystems. Yet, asymmetric encryption is relatively slower and computationally intensive, and requires certificate authority  . File Header It is a common practice of appending metadata containing owner ID, size, last modified time, and location of all data blocks, etc., as a header with the data block. The size of this header varies depending on how much header information is to be stored. The DICOM standard allows image information object definitions that a DICOM file not only contains pixel data but also key information about the image [40] . Thus, a single DICOM file contains both a header and all of the image data. Conventionally, each DICOM medical image is associated with a patient's private data such as patient's name, age,  . It is possible to generate two datasets with different content but having the same message-digest algorithm 5 (MD5) hash  . Cryptographic hash function is extremely bit sensitive to the input   . Perceptual hashing Perceptual hashing usually requires searching for match and access to a central database, where a large amount of pre-computed perceptual hashes are stored BIB001 . Most randomization methods in perceptual hashing are linear, which introduces security flaws as known input/hash pairs can be used to recover a secret key BIB007 . Their quantization and encoding stages require the learning of appropriate quantization thresholds. The quantizer training as well as the storage of thresholds introduces additional security weaknesses. results of examination/diagnosis, time taken, etc. All these private information are recorded into a meta-data or header file, which is appended to the image. The DICOM standard stores the image data and the meta-data separately. Clearly, this is dangerous as the link between the image and the textual information is practically non-existent BIB008 . For example, for the images with plain-text file-header, the major threat is the violation of the access rights and of the daily logs by the intruder. Hence, breaking of the confidentiality implies that integrity and authenticity of the data cannot be guaranteed anymore BIB001 . Furthermore, for an encrypted header, the bit error sensitivity may result in loss of header and/raise further complexity in managing the medical images. Thus, at the least, the patients' private data in a DICOM image are at risk of happenings of a mismatch (i.e., linking of meta-data with an incorrect medical image) and of disclosure and loss of header or meta-data in an image undergoing some intentional processing. Cryptographic Hash Function A cryptographic hash function is a deterministic procedure that takes an arbitrary block of data and returns a fixed-size bit string, the (cryptographic) hash value, such that an accidental or intentional change to the data will change the hash value  . The data to be encoded is often called the message, and the hashes are sometimes called the message digest or simply digest [42]. The ideal cryptographic hash function has four main properties  : (1) it is easy (but not necessarily quick) to compute the hash value for any given message; (2) it is infeasible to generate a message that has a given hash; (3) it is infeasible to modify a message without changing the hash; and (4) it is infeasible to find two different messages with the same hash. Cryptographic hash functions have many information security applications, notably in DS, MACs, MDCs, and other forms of authentication [42] . They can also be used for other purposes such that indexing data in hash tables, fingerprinting, detecting duplicate data and accidental data corruption, etc [42] . Indeed, in information security contexts, cryptographic hash values are sometimes called (digital) fingerprints, checksums, or just hash values, even though all these terms stand for functions with rather different properties and purposes [42] . In addition, most of the existing cryptographic hash function schemes unfortunately remain vulnerable to incidental modifications (i.e., even a one bit change in the input will change the output hashes dramatically)  . This severely limits their practical utility in robust content authentication for multimedia applications. Perceptual Hash Function Perceptual hash functions (or, robust perceptual hash function, or simply, perceptual hashing) are designated hash functions for multimedia contents. This type of hash function takes a large digital image as input, and with constructing a content descriptor of the input, outputs a fixed length binary vector known as hash value. This hash value is required to be invariant under changes to the image that are perceptually insignificant whereas, on perceptually distinct inputs, the hash values need to be approximately independent and hence different with high probability  . . That is, unlike getting a very different hash value from a single bit change in the input of the cryptographic hash function, perceptual hashes are expected to be different only with the changes in the perceptual content of the input. For instance, the hash value of an image and its JPEG compressed version should be the same for the perceptual hash function, since they have no perceptual difference, although their bit-string representation is completely different [45] . Generally, perceptual hashing consists of feature extraction and randomization that introduces non-invertibility and compression followed by quantization and binary encoding to produce a binary hash output. Most randomization methods are linear, and this introduces security flaws because known input/hash pairs can be used to recover a secret key BIB007 . Furthermore, the quantization and encoding stages require the learning of appropriate quantization thresholds, and the quantizer training as well as the storage of thresholds that introduce additional security weaknesses. Moreover, content-based feature extraction methods, developed from a signal processing perspective, are known to be robust but not secure  . Kalker  described perceptual (or robust) hashing from the perspective of a neural archiving activities using clever signal processing and database techniques. The former is responsible for extracting essential perceptual features (also referred to as perceptual hash values or hash values for short), the latter for storing and searching large amounts of pre-computed hash values. Kalker also exemplified with a typical scenario, where a local client (e.g., a mobile phone) is responsible for capturing the content and transmitting the content (possibly only the hash values if the client is equipped with a feature extractor) to a central database. The central database matches the hash values of the unidentified content with the pre-computed hash values, retrieves the best match, and takes appropriate action (e.g., sending an artist name and song title in an SMS message to the requesting client). Reviewing some key existing security measures as discussed above, it can be said that they are useful in handling the common security problems of the system. Yet, their limitations suggest that they are no longer sufficient to provide the required security of the medical information in teleradiology. Therefore, as the new security problems are arising from the advances of technology and developments of PACS/RIS mentioned in "Introduction," new measures are required to be developed and deployed for the improved security of medical images and EPHI. Hence, studies show that digital watermarking can be promising to facilitate sharing and remote handling of that information in teleradiology in a secure manner  BIB005 BIB003 , though a reasonable justification of watermarking applicability for medical images is lacking.