WATERMARKING OF SINGLE AND MULTI FRAME …umpir.ump.edu.my/15257/1/FSKKP - GRAN BADSHAH - CD...
Transcript of WATERMARKING OF SINGLE AND MULTI FRAME …umpir.ump.edu.my/15257/1/FSKKP - GRAN BADSHAH - CD...
WATERMARKING OF SINGLE AND MULTI FRAME ULTRASOUND
MEDICAL IMAGES
GRAN BADSHAH
Thesis submitted in fulfillment of the requirements
for the award of the degree of
Doctor of Philosophy in Computer Science
Faculty of Computer Systems and Software Engineering
UNIVERSITI MALAYSIA PAHANG
FEBRUARY 2016
vii
ABSTRACT
Digital communication of medical images may cause image manipulation for non-
mandatory purposes. The originality of single and multi-frame medical images is
strictly required to be used for patient health recovery. Watermarking is one of the latest
security techniques, which can be used for protection of digital images. This dissertation
has focused on watermarking of grayscale eight bits single and multi-frame ultrasound
medical images. Watermarking of a medical image with heavy payload causes image
degradation and directly affects patient diagnosis. Therefore, watermark must be
lossless compressed to reduce its size without data loss. In the past Lempel-Ziv Welch
(LZW) has been used for text, image pixel data lossless compression and in this
research we extend this technique to binary watermark lossless compression to enhance
the performance of region based watermarking techniques. In region based
watermarking, an image is divided into region of interest (ROI) and region of non-
interest (RONI). LZW compressed watermark based, a new region based watermarking
scheme, tamper detection and recovery watermarking of medical images (TDARWMI)
is developed. Produced results of the scheme are compared with those of other
watermarking schemes and are found better in compression ratio, PSNR of
watermarked and recovered images. In region based watermarking schemes, the tamper
detection and recovery is restricted to ROI, while rest of the image remains under
security threats. Possible wrong selection of ROI is another limitation of region based
watermarking schemes. Non-proper selection of ROI may create problems during
recovery at destination and can affect the required analysis. Therefore, another
watermarking scheme, whole image authentication, tampers detection, localization and
complete recovery (WIATDACR) is developed to provide security to a complete image.
The LZW compressed watermark is embedded into image’s ROI and RONI parts
randomly. At destination, watermark is extracted and used for image authentication,
tampers detection, localization and lossless recovery. This scheme can locate tampers
occurred at any part of image and can perform recovery without data loss. The signature
based security technique of DICOM multi-frame images has deficiency in tamper
detection and recovery. Multi-frame image authentication, tamper detection,
localization and recovery (MFATDLAR) watermarking scheme is formulated to
facilitate a DICOM image’s frame-wise authentication, tamper detection and lossless
recovery. In this scheme the watermark of every frame is prepared, compressed and
encapsulated into respective frame’s RONI part. At destination the extracted watermark
is used for the frame’s authentication, tamper detection, localization and lossless
recovery.
viii
ABSTRAK
Komunikasi digital imej perubatan boleh menyebabkan manipulasi imej untuk tujuan
bukan mandatori. Tunggal dan multi-frame imej perubatan keaslian adalah dilarang
sama perlu digunakan untuk pemulihan kesihatan pesakit. Watermarking adalah salah
satu teknik keselamatan yang terkini, boleh digunakan untuk perlindungan imej digital.
Disertasi ini telah memberi tumpuan kepada watermarking skala kelabu lapan bit
tunggal dan multi-frame ultrasound imej perubatan. Watermarking daripada imej
perubatan dengan muatan berat menyebabkan degradasi imej dan secara langsung
memberi kesan diagnosis pesakit. Oleh itu, watermark mesti lossless dimampatkan
untuk mengurangkan saiznya tanpa kehilangan data. Lalu Lempel-Ziv Welch (LZW)
telah digunakan untuk teks, imej piksel mampatan lossless data dan dalam kajian ini
kita melanjutkan teknik ini kepada perduaan mampatan lossless watermark untuk
meningkatkan prestasi teknik watermarking rantau berasaskan. Di rantau berdasarkan
watermarking, imej dibahagikan kepada kawasan kepentingan (ROI) dan rantau bukan
faedah (RONI). LZW watermark dimampatkan berasaskan, skim watermarking
berdasarkan kawasan baru, pengesanan bega dan pemulihan watermarking imej
perubatan (TDARWMI) dibangunkan. Keputusan yang dihasilkan skim ini
dibandingkan dengan keputusan skim watermarking lain dan didapati lebih baik dalam
nisbah mampatan, PSNR imej tera air dan didapatkan. Dalam skim watermarking rantau
berdasarkan pengesanan bega dan pemulihan adalah terhad kepada ROI, manakala
selebihnya imej kekal di bawah ancaman keselamatan. pemilihan salah kemungkinan
ROI adalah satu lagi had skim watermarking rantau berasaskan. Bukan betul penandaan
ROI boleh menimbulkan masalah di tempat tujuan dan boleh memberi kesan kepada
analisis yang diperlukan. Oleh itu, satu lagi skim watermarking, pengesahan imej
keseluruhan, mengganggu pengesanan tepat dan lengkap pemulihan (WIATDACR)
dibangunkan untuk menyediakan keselamatan untuk imej yang lengkap. The LZW
watermark dimampatkan tertanam ke dalam ROI imej dan bahagian-bahagian RONI
rawak. Di destinasi tera air diekstrak dan digunakan untuk pengesahan imej,
mengganggu pengesanan tepat dan pemulihan lossless. Skim ini boleh mengesan
mengganggu berlaku di mana-mana bahagian imej dan boleh melakukan pemulihan
tanpa kehilangan data. Keselamatan berdasarkan tandatangan DICOM imej pelbagai
bingkai mempunyai pengesanan bega dan kekurangan pemulihan. DICOM skim
pengesahan imej multi-frame, pengesanan bega, penyetempatan dan pemulihan
watermarking (MFATDLAR) dibangunkan untuk membuat mungkin setiap pengesahan
bingkai imej ini, pengesanan bega dan pemulihan lossless. A watermark setiap bingkai
disediakan, dimampatkan dan dimuatkan ke dalam bingkai masing RONI bahagian. Di
destinasi watermark yang diekstrak digunakan untuk pengesahan bingkai, pengesanan
bega, penyetempatan dan pemulihan lossless.
ix
TABLE OF CONTENTS
Page
SUPERVISOR’S DECLARATION iii
STUDENT’S DECLARATION iv
DEDICATION v
ACKNOWLEDGEMENTS vi
ABSTRACT vii
ABSTRAK viii
TABLE OF CONTENTS ix
LIST OF TABLES xiii
LIST OF FIGURES xiv
LIST OF ALGORITHMS xx
LIST OF ABBREVIATIONS xxi
CHAPTER 1 INTRODUCTION
1.1 INTRODUCTION 1
1.2 WATERMARKING POSITION IN HIERARCHY OF DATA
SECURITY TECHNIQUES
5
1.2.1 Secret Key 8
1.2.2 Robust Watermarking 8
1.2.3 Fragile Watermarking 9
1.2.4 Semi-Fragile Watermarking 9
1.2.5 Visible and Invisible Watermarking 9
1.3 WATERMARKING DOMAINS 9
1.3.1 Frequency Domain 10
1.3.2 Spatial Domain 10
1.4 BASIC REQUIREMENTS FOR A DIGITAL IMAGE
WATERMARKING SYSTEM
10
1.4.1 Perceptual Quality 10
1.4.2 Security 11
1.4.3 Capacity 11
1.4.4 Blind and Non-blind Watermarking 11
x
1.5 TELERADIOLOGY AND ITS IMPORTANCE IN
HEALTHCARE
12
1.6 COMPRESSION’S IMPORTANCE IN IMAGE
WATERMARKING
12
1.6.1 Lossy and Lossless Compression 13
1.7 PROBLEM STATEMENT 13
1.8 RESEARCH OBJECTIVES 14
1.9 SCOPE OF RESEARCH 14
1.10 THESIS STRUCTURE 15
CHAPTER 2 LITERATURE REVIEW
2.1 INTRODUCTION 16
2.2 DIGITAL IMAGING 16
2.3 HISTORICAL OVERVIEW OF WATERMARKING 18
2.4 CLASSIFICATION OF WATERMARKING TECHNIQUES 19
2.4.1 Domain Based Watermarking 20
2.4.2 Technical Based Image Watermarking 23
2.4.3 Watermark Detection Based Watermarking 25
2.4.4 Watermark Security Based Watermarking 26
2.4.5 Watermark Function Based Watermarking 27
2.5 TAMPER DETECTION AND RECOVERY
WATERMARKING SCHEMES OF MEDICAL IMAGES
31
2.5.1 LSB Based Image Watermarking 31
2.6 DATA COMPRESSION 35
2.6.1 Lossy Compression 36
2.6.2 Lossless Compression 36
2.6.3 Watermark Compression in Digital Image Watermarking 37
2.7 CONCLUSION 38
xi
CHAPTER 3 WATERMARK COMPRESSION IN DIGITAL IMAGE
WATERMARKING
3.1 INTRODUCTION 40
3.2 METHODOLOGY 41
3.2.1 Watermark Generation and Compression 41
3.2.2 Watermark Decompression 45
3.3 RESULTS AND ANALYSIS 47
3.4 CONCLUSION 56
CHAPTER 4 WATERMARKING OF SINGLE FRAME
ULTRASOUND MEDICAL IMAGES
4.1 INTRODUCTION 57
4.2 METHODOLOGY 58
4.2.1 Watermark Preparation and Compression 59
4.2.2 TDARWMI Watermarking Scheme 62
4.2.3 Image Tamper Detection, Localization and Lossless
Recovery
78
4.2.4 ROI Authentication 79
4.3 WATERMARKED IMAGE ACCURACY MEASUREMENT 81
4.4 RESULTS AND DISCUSSION 84
4.5 CONCLUSION 85
CHAPTER 5 IMAGE SECURITY USING COMPLETE IMAGE AS
WATERMARK
5.1 INTRODUCTION 86
5.2 BACKGROUND 87
5.3 METHODOLOGY 88
5.3.1 WIATDACR Watermarking Scheme 88
5.3.2 Watermark Preparation, Compression and Image
Watermarking
89
xii
5.3.3 Watermark Extraction and Decompression 92
5.3.4 Tampered Localization and Lossless Recovery 92
5.3.5 Image Authentication 118
5.4 RESULTS AND DISCUSSION 120
5.5 CONCLUSION 120
CHAPTER 6 MULTI FRAME DICOM MEDICAL IMAGES
WATERMARKING
6.1 INTRODUCTION 122
6.2 BACKGROUND 123
6.3 METHODOLOGY 125
6.3.1 MFATDLR Watermarking Scheme 136
6.4 RESULT AND DISCUSSION 138
6.5 CONCLUSION 142
CHAPTER 7 CONCLUSION AND FUTURE WORK
7.1 CONCLUSION 144
7.2 RESEARCH CONTRIBUTIONS 144
7.3 LIMITATION OF THIS RESEARCH 145
7.4 FUTURE WORK 146
REFERENCES 147
AUTHOR’S BIODATA 157
PUBLICATION 158
xiii
LIST OF TABLES
Table No. Title
Page
1.1 Comparison of watermarking, cryptography and
steganography based on their properties
7
2.1 Summary of image watermarking based on classes,
techniques, watermark security, detection and functions
29
3.1 Watermark compression results comparison based on
elements reduction
53
3.2 Watermark compression results comparison based on
compression ratio
55
4.1 Comparison of watermark compression techniques
61
4.2 LZW compression of a watermark including 70*115 size
different image samples ROI compression ratios and PSNR
82
4.3 Eight image samples watermarking with LZW compressed
watermark
83
4.4 TDARWMI comparison with TALLOR-RSMA watermarking
scheme
83
5.1 WIATDACR watermarking scheme segmentation results for
ultrasound medical image sample 1
91
5.2 Details of noises added to image shown in Figure 5.4
94
5.3 WIATDACR watermarking scheme results of ten image
samples
117
6.1 DICOM multi frame image sample 1 frame’s selected ROIs
information
139
6.2 DICOM multi frame image sample 2 frame’s selected ROIs
information
140
6.3 MFATDLR watermarking scheme comparison with other
schemes
142
xiv
LIST OF FIGURES
Figure No. Title
Page
1.1 Ultrasound original image
3
1.2 Ultrasound tampered image
3
1.3 Different components involved with web-based medical
image processing in distributed health care system
4
1.4 Hierarchical structure of data security techniques
5
2.1 Diagrammatic view of eight-bits memory system
32
2.2 Lena image watermarking at (a) 1st LSB (b) using Baboon
image as watermark to get (c) a watermarked image
33
2.3 Lena image watermarking at (a) 7th
bit (b) using Baboon
image as watermark to get (c) a watermarked image
33
2.4 Lena image watermarking at (a) 8th
bit (b) using Baboon
image as watermark to get (c) a watermarked image.
34
2.5 Digital image lossy, lossless compression and
decompression
37
3.1 Example of binary watermark compression using LZW
technique
43
3.2 Example of text data compression using LZW technique
44
3.3 Compressed string lossless decompression using LZW
technique
46
3.4 Ultrasound image sample 1
48
3.5 Ultrasound image sample 2
48
3.6 Ultrasound image sample 3
49
3.7 Ultrasound image sample 4
49
3.8 Ultrasound image sample 5
50
3.9 Ultrasound image sample 6
50
xv
3.10 Ultrasound image sample 7
51
3.11 Ultrasound image sample 8
51
3.12 Ultrasound image sample 9
52
3.13 Ultrasound image sample 10
52
3.14 Watermark elements reduction comparison
54
3.15 Watermark compression ratio comparison
55
4.1 Image watermarking, communication, watermark
extraction and decompression.
59
4.2 Original image sample 1
60
4.3 Curve based comparison of watermark compression
techniques
61
4.4 Watermarked image sample 1
63
4.5 Tampered image sample 1 tampered by adding salt and
pepper noise
63
4.6 Recovered image sample 1
64
4.7 Original image sample 2
64
4.8 Watermarked image sample 2
65
4.9 Tampered image sample 2 tamper by adding cropping
noise
65
4.10 Recovered image sample 2
66
4.11 Original image sample 3
66
4.12 Watermarked image sample 3
67
4.13 Tampered image sample 3 tampered by added 50% noise
67
4.14 Recovered image sample 3
68
4.15 Original image sample 4
68
4.16 Watermarked image sample 4
69
xvi
4.17 Tampered image sample 4 tampered by adding cropping
noise
69
4.18 Recovered image sample 4
70
4.19 Original image sample 5
70
4.20 Watermarked image sample 5
71
4.21 Tampered image sample 5 tampered by adding salt and
pepper noise
71
4.22 Recovered image sample 5
72
4.23 Original image sample 6
72
4.24 Tampered image sample 6 tampered by 99% added noise
73
4.25 Watermarked image sample 6
73
4.26 Recovered image sample 6
74
4.27 Original image sample 7
74
4.28 Watermarked image sample 7
75
4.29 Tampered image sample 7 tampered by adding cropping
noise
75
4.30 Recovered image sample 7
76
4.31 Original image sample 8
76
4.32 Watermarked image sample 8
77
4.33 Tampered image sample 8 tampered by adding salt and
pepper noise
77
4.34 Recovered image sample 8
78
4.35 ROI hash value before image communication
80
4.36 ROI hash value after image communication
80
4.37 ROI hash changed value after image communication
80
4.38 Ultrasound original image sample 1 (b) watermarked
image (c) tampered image (d) recovered image
80
xvii
4.39 Compression results of a watermark including 70*115 ROI
82
5.1 Original ultrasound image sample 1
90
5.2 Original image sample 1 used as a major part of watermark
90
5.3 Segmentation results of image sample 1
91
5.4 Image sample 1 tampered at five different points
93
5.5 Recovered image sample 1
93
5.6 WIATDACR scheme run time for image sample 1
94
5.7 WIATDACR run time results part 1for image sample 1
95
5.8 WIATDACR run time results part 2 for image sample 1
96
5.9 Original ultrasound image sample 2
97
5.10 Original image sample 2 used as a major part of watermark
98
5.11 Image sample 2 tampered at four different points
98
5.12 WIATDACR scheme run time for image sample 2
99
5.13 WIATDACR run time results part 1 for sample 2
99
5.14 WIATDACR run time results part 2 for sample 2
100
5.15 Recovered image sample 2
101
5.16 Original ultrasound image sample 3
101
5.17 Original image sample 3 used as a major part of watermark
102
5.18 Image sample 3 tampered at three different points
102
5.19 Recovered image sample 3
103
5.20 WIATDACR scheme run time for image sample 3
103
5.21 WIATDACR run time results part 1 for image sample 3
104
5.22 WIATDACR run time results part 2 for image sample 3
105
5.23 Original ultrasound image sample 4
106
xviii
5.24 Image sample 4 tampered at three different points
106
5.25 Recovered image sample 4
107
5.26 Original ultrasound image sample 5
107
5.27 Image sample 5 tampered at four different points
108
5.28 Recovered image sample 5
108
5.29 Original ultrasound image sample 6
109
5.30 Image sample 6 tampered at four different points
109
5.31 Recovered image sample 6
110
5.32 Original ultrasound image sample 7
110
5.33 Image sample 7 tampered at four different points
111
5.34 Recovered image sample 7
111
5.35 Original ultrasound image sample 8
112
5.36 Image sample 8 tampered at four different points
112
5.37 Recovered image sample 8
113
5.38 Original ultrasound image sample 9
113
5.39 Image sample 9 tampered at two different points
114
5.40 Recovered image sample 9
114
5.41 Original ultrasound image sample 10
115
5.42 Image sample 10 tampered at three different points
115
5.43 Recovered image sample 10
116
5.44 Graphical results of ten image samples
118
5.45 Sample 1 image hash before watermarking
119
5.46 Sample 1 image hash after watermark extraction
119
5.47 Sample 1 image hash before communication
119
xix
5.48 Sample 1 image hash after communication
119
6.1 DICOM multi-frame image 1 frame 1
126
6.2 DICOM multi-frame image 1 frame 2
126
6.3 DICOM multi-frame image 1 frame 3
127
6.4 DICOM multi-frame image 1 frame 4
127
6.5 DICOM multi-frame image 1 frame 5
128
6.6 DICOM multi-frame image 1 frame 6
128
6.7 DICOM multi-frame image 1 frame 7
129
6.8 DICOM multi-frame image 1 frame 8
129
6.9 DICOM multi-frame image 1 frame 9
130
6.10 DICOM multi-frame image 1 frame 10
130
6.11 DICOM multi-frame image 1 frame 11
131
6.12 DICOM multi-frame image 1 frame 12
131
6.13 DICOM multi-frame image 1 frame 13
132
6.14 DICOM multi-frame image 1 frame 14
132
6.15 DICOM multi-frame image 1 frame 15
133
6.16 DICOM multi-frame image 2 frame 1
133
6.17 DICOM Multi-frame image authentication code generation
and verification
134
6.18 DICOM Multi-frame image division into separate frames
135
6.19 DICOM Multi-frame image watermark extraction and
decryption
136
6.20 DICOM frame authentication verification
137
6.21 Watermarking time graph for DICOM multi-frame images
141
xx
LIST OF ALGORITHMS
Algorithm No. Title
Page
3.1 LZW algorithm for binary watermark compression
42
3.2 LZW algorithm for binary watermark decompression
46
6.1 Watermark preparation and multi-frame DICOM
watermarking 134
xxi
LIST OF ABBREVIATIONS
AES Advance Encryption Standard
ANN Artificial Neural Network
CRC Cyclic Redundancy Check
CT Computed Tomography
Db Decibel
DCT Direct Cosine Transformation
DFT Direct Fourier Transformation
DICOM Digital Imaging and Communication in Medicine
DS Digital Signature
DWT Direct Wavelet Transform
EPR Electronic Patient Record
GIF Graphic Interchange Format
HIS Hospital Information System
IEEE Institute of Electrical and Electronics Engineering
IRVL Image Row Value Length
JPEG Joint Photographic Expert Group
LBP Local Binary Pattern
LSB Least Significant Bit
LZW Lempel-Ziv Welch
MAC Machine Authentication Code
MDC Manipulation Detection Code
MLP Multilayer back Propagation
MFATDLR Multi-frame authentication, tamper detection,
localization and lossless recovery
xxii
MRI Magnetic Resonance Imaging
MSE Mean Square Error
NASA National Aeronautics and Space Administration
NM Nuclear Medicine
PACS Picture Archive and Communication in Medicine
System
PBM Portable Bitmap
PET Positron Emission Tomography
PNG Portable Network Graphics
PSNR Peak signal to noise ratio
RIS Radiological Information System
ROI Region of Interest
RONI Region of Non-Interest
RSMA ROI Segmentation and Multilevel Authentication
SHA Secure Hash Algorithm
SNR Signal to Noise Ratio
TALLOR Tamper Localization and Lossless Recovery
TDARWMI Tamper Detection and Recovery Watermarking of
Medical Images
US Ultrasound
VPN Virtual Private Network
WIATDACR Whole Image as Watermark for Authentication and
Tamper Detection, Localization and Complete
Recovery
CHAPTER 1
INTRODUCTION
1.1 INTRODUCTION
History of the world is a witness of changes in technologies. Changes are made
to upgrade the technologies but some upgradations have negative effects on their related
applications. For example the invention and development of Internet technology has
replaced formal, complex, costly and time consuming data communication system by an
automatic, easy, cheaper and real-time responding one with data security threats.
Internet technology has interconnected people around the globe to store, share, access
and communicate data digitally with chances for hacker’s manipulation. Digitization of
data has facilitated data communication, effective storage, duplication, transportation
with cost reduction. The use of digital technology has replaced data centralized records
storage by decentralized one through globally accessible Internet with increase of
security demands. Easy and open accessibility of Internet data may result into illegal
alteration. Data alteration may happen intentionally and non-intentionally but affect the
achievement of dedicated goals. Data alteration happens due to the unauthorized
accesses or use of noisy communication channels. The illegal change in data originality
is known as tampering. Data tampering causes problems of ownership, integrity,
confidentiality and authentication of data. Digital medical image tampering is a problem
that has been faced in electronic healthcare environment. Due to the lack of security
unwanted outcomes may be produced and can loss the important digital image
information. For more than last two decades, different security measures including
digital watermarking have been tested to solve this problem (Abd-Eldayem, 2013).
Watermarking is an efficient technique to be used for Internet based medical image’s
authentication, tamper detection, localization and lossless recovery.
2
A typical watermark is a meaningful identification mark such as logo,
fingerprint, sequence of text or numbers, a secret code, an image or part of image used
for product identification, ownership proof, authentication and prevention of illegal
distribution, duplication (Holliman and Memon, 2000). A watermark size is not
restricted to a limit and can be long as to cover all the features of a product. Watermarks
can be pasted onto or encapsulated into products for achievement of defined goals. The
process of watermark pasting or encapsulation is called watermarking (Memon, 2010).
Digital medical image security is very important in electronic healthcare system because
pixels of a digital image can be easily manipulated due to easy access to the Internet. A
watermarking technique should have the capability to detect, locate and restore such
manipulations of medical images (Langelaar et al., 2000).
An efficient watermarking technique has the ability to keep the image data under
protection even after image communication and watermark extraction. Watermarking
technique is applicable to audio, video, text, image and other possible digital product. A
product after watermark encapsulation is called watermarked product. For example, the
watermark embedded image is called watermarked image. A watermark is embedded in
a product for the aims of copyright protection, fingerprinting, integration, broadcast
monitoring and authentication (Zhao et al., 2011). Copyright watermarks are used to
prove the product ownership through backtracking, fingerprinting and to determine the
source of illegal distribution. Copy protection watermarks prevent illegal copy of
products while broadcast monitoring watermarks are used to control and ensure the
agreed upon advertisements processing. In data hiding watermarking, the coded data is
hided into a product for its safe sending to destination. In case of medical image
watermarking the code may comprise of image metadata or diagnostic information or
both. If image is tampered during communication then at destination tampers can be
localized and recovered without losing any important data. Different watermarking
techniques are available for image tamper detection, localization and recovery (Nyeem
et al., 2012). These techniques are reviewed in the next chapter of literature review in
details. The remaining chapters explore that how tamper detection, localization and
recovery is performed in our proposed methodologies.
3
Figure 1.1: Ultrasound original image
Figure 1.2: Ultrasound tampered image
Figures 1.1 and Figure 1.2, show the original and its tampered version of an
ultrasound medical image respectively. The tampered image has been obtained from
cropping the original image through the ImageJ software to show it as an example of
image tampering in teleradiology environment. During patient’s diagnosis, if the
4
doctors consider the cropped spot as an original part of image then it will surely mislead
the final results and can put the patient life in danger.
Figure 1.3: Different components involved with web-based medical image processing
in distributed health care system
Figure 1.3 shows a diagram with visible main components used in research work
related to distributed health care system located at Yonsei university of South Korea.
The components links show the access mechanism of a medicle image specialist system
at remote hospitals using satellite technology in telemedicine (Osborne, 2005). This is
an example of picture archive and communication in medicine system (PACS) for the
study of medical images. This system is basically derived from National Aeronautics
and Space Administration (NASA), where the astronaut’s medical information were
collected on earth from space in audio and video formats.
5
1.2 WATERMARKING POSITION IN HIERARCHY OF DATA SECURITY
TECHNIQUES
Data security remains a hot research topic for all the times because new security
measures are needed with evaluation and development of communication technologies.
Data security literature reports a number of techniques used for centralized and
distributed data security. Figure 1.4 shows the hierarchical structure of data security
techniques including watermarking (Cheddad et al., 2010). Data security techniques are
basically divided into two types, cryptography and information hiding.
Figure 1.4: Hierarchical structure of data security techniques
Cryptographic techniques are used to get data in a reduced coded format as
compared to the original data. The code is understandable only to the related people and
remains secured from the outside people’s understanding. Cryptography is a Greek
word means secret writing; different functions are applied to data to get their secret
codes. A MATLAB supported function SHA-256 is an example of such functions.
6
SHA-256 produces a 64-bytes hexadecimal code after application to data. The resulted
code is used mostly for respective data authentication. The main limitation of a
cryptographic technique is the only reporting of data authentication and has no
capability to detect, locate and recover the tampers. Information hiding based security
techniques are used to hide important information within a product. Hiding of an image
data into image itself is an example of information hiding. The image serves as a carrier
of hided data to be used at destination for intended purpose. Information hiding
techniques are further divisible into steganography and watermarking. Steganography is
also a Greek word means covered writing. Steganography data is the actual data hidden
into a carrier without resulting into coded form like cryptography. Steganography aims
to transfer secret data to destination with high security. A carrier medium is cared
highly for the successful delivery of secret data and does not remain important after the
hidden data extraction.
Watermarking is also a data hiding technique, capable to hide and extract
information with intensive care of medium because medium remains the main focus of
watermarking process. For example a medical image watermark is used for image
authentication, tamper detection, localization and recovery. The actual mean of a
medical image watermarking is to ensure the image originality for patient health
analysis. During watermarking, the important data is hided into images, audios, videos
and texts as watermarks according to the requirements. A watermarking technique is
robust or fragile in nature; robust watermarking focuses on watermark security while
the fragile one is used for product contents security. Imperceptibility, visibility and
fingerprinting describe different levels and types of image watermarking.
Imperceptibility means how to make a watermark data non-influential to the originality
of an image. Visibility means how to keep a watermark data invisible to the human
sight to increase its security. Fingerprinting is used to back-track the process of data
illegal distribution to reach the illegal distributor of important data. A secret key can be
used for making a watermarking scheme more secured and efficient.
7
Table 1.1: Comparison of watermarking, cryptography and steganography based on
their properties
S.no Property Watermarking Cryptography Steganography
1 History Modern era, started after
the creation of digital
images
Modern era but
earlier than digital
watermarking
Ancient, invented
before the creation
of digital images
2 Secret data Watermark Plain text Payload
3 Secret carrier Image, audio and video
files
Image and text Any digital and
non-digital media
4 Key Optional Necessary Optional
5 Input file At least one Always one At least one
6 Detection Blind or non-blind Blind Blind
7 Result Watermarked image or
file
Cipher text or
image
Stego image or file
8 Main
purpose
Authentication, tamper
detection, Recovery and
copyrights protection
Data authentication Data secret
communication
9 Visibility Visible and non-visible Always visible Always non-visible
10 Failure If removed, demaged or
altered
If decrypted If detected
11 Choice of
carrier
selection
Restricted to focused
image, video or audio
file
Not available Not restricted to a
specific carrier
12 Carrier and
secret data
relationship
Carrier is more
important while secret
data remains its
important attribute
No relation at all Secret data is more
important than
carrier
13 Attack
causes
Image processing
operations
Cryptanalysis Stego analysis
14 Main
concern
Robustness Robustness Capacity