image encryption using chaotic based cryptosystem
TRANSCRIPT
IMAGE ENCRYPTION USING CHAOTIC BASED CRYPTOSYSTEM
MUHAMAD LUQMAN NULHAKIM BIN MANSOR
BACHELOR OF COMPUTER SCIENCE (COMPUTER NETWORK SECURITY)
WITH HONORS
FACULTY OF INFORMATICS AND COMPUTING
UNIVERSITI SULTAN ZAINAL ABIDIN, TERENGGANU, MALAYSIA
MAY 2019
i
CONFIRMATION
This Image Encryption using Chaotic Based Cryptosystem project report was
prepared and submitted by Muhamad Luqman Nulhakim bin Mansor (BTBL16043975)
and has meet the satisfactory in terms of scope, quality and presentation as partial
fulfillment of the requirement for the Bachelor of Computer Science (Computer
Network Security) with honours in University of Sultan Zainal Abidin.
Signature: …………………………………….
Supervisor: Prof Madya Dr. Afendee bin Mohamed
Date: .……………………………………
ii
DECLARATION
This dissertation is submitted as a partial fulfilment for receiving a Bachelor of
Computer Science (Computer Network Security) with honours at University of
Sultan Zainal Abidin, Terengganu. The work is a result of my own research and
study. Texts, and results for all section was obtained from other sources, are fully
referenced.
Signature : …………………………………….
Name : Muhamad Luqman Nulhakim bin Mansor
Date : …………………………………….
iii
ACKNOWLEDGEMENT
Alhamdulillah, in the Name of Allah, the Most Gracious and the Most Merciful.
This project could not have been conducted without the support, encouragement
and cooperation of many people. First of all, I would like to thanks to my supervisor,
Prof Madya Dr Afendee bin Mohamed who always supported and gave good ideas in
this project. I would like to thank her for giving the opportunity to learn under her
guidance, which has been the most memorable experience.
I would also like to take this opportunity to thank to my parents, friends and special
thanks to all lecturers of faculty of Informatics and Computing for their guidance and
good advice to help in the implementation of this project. May Allah S.W.T bless all
the effort that has been taken to finish this project.
Thank you.
iv
ABSTRAK
Ini merupakan satu kajian yang telah dijalankan untuk menghasilkan projek dimana
ianya adalah mengenai Penyulitan Gambar menggunakan Kriptosistem berasaskan
Chaotic. Tujuannya adalah untuk mencipta satu persekitaran dimana penyulitan
gambar mempunyai unsur tambahan dengan mengadaptasikan ciri-ciri teori chaos.
Implementasi teori chaos didalam kriptosistem ini, dimana ia mempunyai elemen
yang tidak menentu dan sangat sensitif pada nilai awalan sesuatu perkara. Penyulitan
ini menggunakan kaedah kunci simetrik. Penjanaan kunci untuk setiap pixel gambar
diambil dari peta chaotic. Peta chaotic adalah satu fungsi matematik tidak linear
yang mengadaptasi elemen chaos, elemen yang tidak menentu, dan rawak
berdasarkan nilai awalan sesuatu perkara. Jika keadaan awalan berubah, ia akan
mengubah nilai akhir untuk fungsi tersebut. Tambahan pula, penyulitan ini dapat
membantu dalam menghasilkan satu persekitaran perkongsian gambar yang selamat
melalui rangkaian terbuka. Hal ini kerana data daripada gambar dan teks boleh
digodam oleh penggodam dalam rangkaian tersebut.
v
ABSTRACT
This paper is a research on the proposed project about Image Encryption using Chaotic
Based Cryptosystem. The purpose is to create an image encryption environment with
additional features that exhibits from chaos theory. Where the element of uncertainty
and sensitive to initial condition is applied in this cryptosystem. This encryption used
symmetric key, where the key generation for every pixels of image use from chaotic
map. Chaotic map is a non-linear mathematical function that exhibit the uncertainty and
randomness based on the initial values. If the initial conditions change it will affect the
outcome result for the function. Furthermore, this encryption is to help to create a secure
image sharing environment via public network. This is because the image data or text
data can be tapped or eavesdropped by unwanted users in the network.
vi
TABLE OF CONTENT
CONFIRMATION ...................................................................................................................... i
DECLARATION ....................................................................................................................... ii
ACKNOWLEDGEMENT ........................................................................................................ iii
ABSTRAK .................................................................................................................................. iv
ABSTRACT ............................................................................................................................... v
TABLE OF CONTENT ............................................................................................................ vi
LIST OF FIGURES ................................................................................................................ viii
LIST OF TABLES ................................................................................................................... xii
LIST OF ABBREVITIONS .................................................................................................... xiii
LIST OF FORMULAE ........................................................................................................... xiv
Chapter 1 .................................................................................................................................... 1
1.1. Background ................................................................................................................ 1
1.2. Problem Statement ..................................................................................................... 3
1.3. Objective .................................................................................................................... 4
1.4. Scope .......................................................................................................................... 4
1.5. Limitation of Work .................................................................................................... 4
1.6. Summary .................................................................................................................... 5
Chapter 2 .................................................................................................................................... 6
2.1. Introduction ................................................................................................................ 6
2.2. Chaos Theory and Chaotic Based Crypto-system ...................................................... 7
2.3. Previous Research .................................................................................................... 10
2.4. Summary .................................................................................................................. 16
Chapter 3 .................................................................................................................................. 17
3.1. Methodology ............................................................................................................ 17
3.2. Defining Phase ......................................................................................................... 18
vii
3.2.1. Field of Study ................................................................................................... 19
3.2.2. Software Requirement ...................................................................................... 20
3.3. Planning Phase ......................................................................................................... 21
3.4. Designing Phase ....................................................................................................... 22
3.3.1. Flowchart Encryption ....................................................................................... 23
3.3.2. Flowchart Decryption ...................................................................................... 24
3.4. Development Phase .................................................................................................. 25
3.4.1. Encryption Phase .............................................................................................. 25
3.4.2. Decryption Phase ............................................................................................. 32
3.5. Analysis Phase ......................................................................................................... 36
3.5.1. Key Sensitivity Analysis .................................................................................. 37
3.5.2. Statistical Analysis (Histogram) ...................................................................... 38
3.5.3. Statistical Analysis (Correlation and Coefficient) ........................................... 40
3.5.4. Fixed Point Analysis ........................................................................................ 41
3.5.5. Intensity Analysis ............................................................................................. 41
3.6. Summary .................................................................................................................. 42
4.1. Introduction .............................................................................................................. 43
4.2. Cryptographic Scheme ............................................................................................. 43
4.2.1. Image Encryption Cryptosystem Scheme ........................................................ 44
4.2.2. Image Decryption Cryptosystem Scheme ........................................................ 47
4.3. Simulation ................................................................................................................ 49
4.3.1. Encryption Process ........................................................................................... 49
4.3.2. Decryption Process .......................................................................................... 53
4.4. Result Analysis ........................................................................................................ 56
4.4.1. Image Channel Analysis .................................................................................. 56
4.4.2. Image Histogram Analysis ............................................................................... 58
5.1. Summary .................................................................................................................. 63
References ................................................................................................................................ 65
viii
LIST OF FIGURES
FIGURE TITLE PAGE
1 Pixel Size in 2.54 centimetre 5
2 Chaotic System’s Characteristics 8
3 Relationship of Chaos Theory and Cryptography 9
4 Histograms of the Plain Image and Encrypted Image 11
5 Model Encryption of Region Based Selective Image
Encryption
12
6 Region-based Encryption Result 13
7 Project Methodology 17
8 Defining Field of Study 18
9 General Overview of Proposed Cryptosystem 21
10 Encryption Operation for Proposed Cryptosystem 23
11 Decryption Operation for Proposed Cryptosystem 24
12 Input Plain-image and Image Channel Separation 25
13 Process for Image Channel Separation 26
14 Chaos Sequence Key Generation 26
15 Rossler System’s Equation (1) 27
16 Pixels Illustration 27
17 Channel Encryption 28
18 RGB Channel of Lena.png 29
19 Image Channel Merger 29
20 Process after Encryption for Different Image Channels 30
21 Outcome from Image Merger Operation 30
ix
22 Overview for Cipher-image and Key Distribution 31
23 Input Cipher-image, Input Key, and Image Channel Separation 32
24 Operation for Image Channel Separation 33
25 Reverse Channel Encryption 34
26 Operation for Reverse Channel Encryption 34
27 Image Channel Merger and Plain Image 35
28 Operation for Image Channel Merger and Plain Image 36
29 Key Sensitivity Analysis 37
30 Statistical Analysis Histogram of Greyscale Image 38
31 Statistical Analysis Histogram of RGB Channel Image 39
32 Statistical Analysis Correlation and Coefficient of the
Greyscale Image
40
33 Intensity Analysis Tampered Images as Input) 42
34 Pixel (1, 1) Representation for Lena.png 44
35 Rossler Sequence Generation 45
36 Encryption Process for each Channels 45
37 Lena.png after Encryption in 3 Different Channels 46
38 Decryption Process for each Channels 47
39 Lena.png after Decryption in 3 Different Channels 48
40 Encryption Flow (i) – Menu Interface 49
41 Encryption Flow (ii) – Upload Image Interface 50
42 Encryption Flow (iii) – Preview Image Upload Interface 50
43 Encryption Flow (iv) – Image Channel Separator Preview
Interface
51
44 Encryption Flow (v) – Image Encrypted Interface 51
x
45 Encryption Flow (vi) – Time Taken for Encryption Status 52
46 The Encrypted Image and Key for the Image 52
47 The Content of encryptedimg.txt 53
48 The Content of key.txt 53
49 Decryption Flow (i) – The Upload Encrypted Image and Key
Interface
54
50 Decryption Flow (ii) – The File Selection Interface 54
51 Decryption Flow (iii) – Encrypted Image Preview Interface 55
52 Decryption Flow (iv) – Image Decrypted Preview Interface 55
53 Decryption Flow (v) - Time Taken for Decryption Status 55
54 Folder Contain Files during Process Encryption and
Decryption
56
55 Image Channel Analysis (i) – Image Preview Interface 57
56 Image Channel Analysis (ii) – Split Channels Option Interface 57
57 Image Channel Analysis (iii) – RGB Channels Preview for the
Encrypted Lena.png
58
58 Image Histogram Analysis (i) – Example Histogram Analysis. 59
59 Image Histogram Analysis (ii) – Inputs for Histogram Analysis 59
60 Image Histogram Analysis (iii) – Grayscale Histogram for
Lena.png
60
61 Image Histogram Analysis (iv) – Extract Histogram Lena.png
in MATLAB
60
62 Image Histogram Analysis (v) – Grayscale Histogram for
Encrypted Lena.png
60
xi
63 Image Histogram Analysis (vi) – Extract Encrypted Lena.png
in MATLAB
61
64 Image Histogram Analysis (vii) – RGB Histogram
Representation Lena.png
61
65 Image Histogram Analysis (viii) – Extracting Lena.png in
MATLAB
62
66 Image Histogram Analysis (ix) – RGB Histogram
Representation Encrypted Lena.png
62
67 Image Histogram Analysis (x) – Extracting Encrypted
Lena.png in MATLAB
62
xii
LIST OF TABLES
TABLE TITLE PAGE
1 Research about AES Based for Image Encryption 10
2 Entropies of Encrypted Image of Mickey Image.bmp 11
3 Correlation Coefficient of Two Adjacent Pixels in Original and
Encrypted Image
11
4 Performance of AES and Modified AES Encryption 12
5 Research about Region Based Image Encryption 13
6 Research about Image Encryption using Block-Cipher 14
7 Research about Image Encryption with Hybrid Chaotic Systems 14
8 Research about Image Encryption using AdvHill Cipher 15
xiii
LIST OF ABBREVITIONS
ABBREVIATION EXPLANATION
AES Advanced Encryption Standard
2D Two-Dimensional
AdvHill Advanced Hill
IDE Integrated Development Environment
RGB Red, Green, Blue
PNG Portable Network Graphics
xiv
LIST OF FORMULAE
FORMULA TITLE PAGE
1 General Formula Encryption using Chaotic Based 44
2 Detailed Formula Encryption using Chaotic Based 46
3 General Formula Decryption using Chaotic Based 47
4 Detailed Formula Decryption using Chaotic Based 48
1
Chapter 1
Introduction
1.1. Background
As time goes by, humans and machine interaction become famous from sharing
general data to confidential data. These data we talk about, came in different type like
video, audio, text, and image. Usually we don’t really care what the consequences from
exposing general data to wrong person or someone eavesdropping the data. But when it
comes to confidential data that is going to have a serious problem when people exploit
the confidentiality of data.
That is when computer scientist and mathematician came up with the idea of masking
the real message or we call it encryption. Encryption is a technique use to scramble the
original content of messages (data) before transferring. In order to read an encrypted
data, one shall decrypt the encrypted data into its original content. In this proposed
project, I’m going to specify my scope to image data type. The idea is to create an image
encryption using a chaos based algorithm. In order to work on this new
multidisciplinary field, the challenge is to propose a new algorithm of encryption and
decryption that maximize the security and lessen the potential of attacker to retrieve
information from images [1].
2
As the fundamental of securing a data, there will be a key that help to lock (encrypt)
and unlock (decrypt) the data. The image encryption is a method to hide the information
contains in the image.
The idea is to exhibit the behaviour and characteristic of chaos theory where chaos
theory is famous with it randomness and deterministic. Where the initial condition of
the system will affect the behaviours of the system. That means one simple changes
might affect the most part of the result.
The process of encryption and decryption using a chaos based algorithm for this
proposed project will be explain further detail in Chapter 3, the methodology part of the
project. This idea was developing and come out from multiple research by choosing a
suitable chaos based algorithm where it can help to encrypt the data that contain in
image file.
3
1.2. Problem Statement
Nowadays, information security is become more important especially when it comes to
transmission of confidential data to other person or even store it for your own use.
Usually this problem will relate to the process of transferring data via public network.
The hacker can eavesdrop on every single packet movement (the data transmission
process) on the network. He can retrieve the data and have all the confidential
information from you without our conscious.
If we apply an image encryption before sending it to desired person via public network.
He/she the eavesdropper have a hard time trying to figure out how to read the data from
image. Storing personal or confidential data can be a bit challenging where people have
access to our machine (computer or laptop). Yes, creating a specific folder won’t help
much in preserving the confidentiality of the data. In this way, people have hard time to
save images in a places where people can discover it easily.
a) Image data has been widely being used in many industry and it has been used
for many private data
b) Storing image data locally, can be less secure. Because the image only being
stored without any security measure applied.
c) When transferring data via public network, data such as text or images can be
tapped and eavesdropped from unwanted person.
4
1.3. Objective
a. To apply a suitable chaotic map for encryption
b. To develop an image encryption based on chaotic cryptography
c. To evaluate the performance of the cryptosystem
d. To create a secure image sharing environment
1.4. Scope
This proposed project is to create an encryption for the user that want to secure the
image before sharing or user that want to save data locally. This consists medium
users, students and also corporation that want to save their image data in a reliable
way.
1.5. Limitation of Work
The limitation of this proposed project, is depend on the image. The higher the
resolution of the image, the more amount of pixel cover in certain region, refer
Figure 1. That means that is a lot of time taken in the encryption process. The
encryption is still possible but in the time measurement, it might take a while.
5
Figure 1: Pixel Size in 2.54 centimetre
1.6. Summary
This chapter describes about a few topics that should be included in introduction of
projects such as background of project, problem statements, objectives, scope, and
limitation of work. Thus it helps to organize a better documentation of the project.
6
Chapter 2
Literature Review
2.1.Introduction
This section describes the theory, techniques and concepts that were studied in order
to create an understanding on the problem and how researcher come out with
method to solve the problem. Generally speaking, encryption is a method to ensure
the confidential of data is taken care during file sharing through open network or
save into personal storage locally [2]. Decryption basically is a method to open the
encrypted data. However in this proposed project I use the cryptosystem towards
image encryption. The image encryption is the ability to hide the interpretation data
in real image (from plain-image to cipher-image).
This is to help protecting the original form of data that contains valuable information
[3]. Furthermore, it also help from unauthorised access from non-receiver for the
data and increase the reliability from being attack by any kind cryptanalysis attack.
In addition, the image encryption method is based on chaotic cryptosystem. Where
the encryption process need to be set with an initial values to be a parameters in
chaotic map. Where the random-like behaviours of the system and sensitivity of
data based on initial values [4]. In term of security models and cryptosystem that
7
based on number theory and chaotic map, most of it has been proposed and research
found that some of them are either inefficient based on performance or weak in scale
of computational complexity and security [5-7]. In this chapter we will see literature
discussion from previous research that have co-related with the proposed project
characteristic. The discussion will be touch in image encryption, chaotic map, and
how the researcher optimizing their work in order to have a better solution to get rid
of problem in image encryption.
2.2.Chaos Theory and Chaotic Based Crypto-system
The chaos theory, in a simple term is a process where the system behaviours are
based on initial condition of the system or also can be called sensitive dependency
to the initial conditions. To make an example for the chaos theory, let say a system
that predict the future forecast might need several of initial inputs to create accurate
prediction. But once the system altered the inputs during process, it will behave in
a way that we don’t expect it to be. That means, even with a small difference from
the input might change the behaviour of the system itself [8]. That is chaos. Beside
from weather forecast, chaos theory have more practical applications in many
industry such as sciences, physics, dynamical systems, non-periodic order, and
mathematics [9]. But in this situation, we will see the implementation of chaos
theory in mathematics and might be a part of physics and those implementation will
create a chaotic system.
8
To be more specific, a chaotic system must be equivalent to these characteristics
[12].
Figure 2: Chaotic System’s Characteristics
Based on Figure 2, we will go through the characteristic of chaotic system. The
first characteristic is nonlinearity, nonlinearity means that the change in an element
at initial time can bring to a change in the same or different element at later time.
It is not depend on the change at the initial time. The next thing is, determinism.
Deterministic means that the system is governed or based on rules and does not
exhibit the element of chances. Meaning that, the system behaviour will behave
from the previous cause or the initial value.
By that, we can tell that chaotic system is a system that sensitive to the initial
condition. The trajectories of variables in chaotic system was pre-defined by initial
parameters. The changes of condition during the system execution, might not give
the same result of the final outcome.
Nonlinearity Determinism Sensitivity to initial
conditions
Long-term Prediction Irregularity
9
Talking about outcome, one of the chaotic system is their long-term prediction
characteristic. The outcome from the initial condition cannot be easily predict.
Because we were controlled by the initial conditions of the system, which can only
be known to a finite degree of precision.
Figure 3: Relationship of Chaos Theory and Cryptography
Before you get to know what chaotic based crypto-system is, there is something
you need to know. The invention of chaotic based cryptosystem was came up from
the idea of exhibiting the chaos theory and implement it in cryptosystem refer to
Figure 3.
Chaos Theory Cryptography
Chaos-Based Cryptography
10
2.3. Previous Research
In this field that I have studied, consist many related research in image encryption
and the application of chaos theory in the cryptosystem. Among the researches, I
choose five (5) of it. The first research is from Seyed Hossein Kamali, and Reza
Shakeria as seen in Table 1.
Author Title Description Method
Seyed Hossein Kamali, Reza Shakeria
A New Modified Version of Advanced Encryption Standard Based Algorithm for Image Encryption
An encryption technique using Symmetrical Encryption and ShiftRow transformation based on a modified version of AES
Modified Version of AES; ShiftRow Transformation and Symmetrical Encryption
Table 1: Research about AES Based for Image Encryption
In this encryption method, the application of AES is applied in the ShiftRow
transformation [11]. In the ShiftRow Transformation for this paper, if the first row and
the first column is even, it will stay. But when the third and fifth rows of the state, it
will cycle and shifted to left or to the different number. This encryption performance
analysis has been recorded from aspect of image histogram of encrypted image (Refer
Figure 4), information entropy analysis (Refer Table 2) and correlation coefficient of
two adjacent pixels in original and encrypted image (Refer Table 3) [3,10,13].
11
Figure 4: Histograms of the Plain Image and Encrypted Image
Encryption Algorithm Entropy Value
AES 7.9989
Modified AES 7.9992
Table 2: Entropies of Encrypted Image of Mickey Image.bmp
Direction Plain image Cipher image
Horizontal 0.9452 -0.0112
Vertical 0.9471 -0.0813
Diagonal 0.9127 0.0009
Table 3: Correlation Coefficient of Two Adjacent Pixels in Original and Encrypted Image
The modification that implement to the AES by adjusting ShiftRow Transformation. The
performance of AES and Modified AES were recorded (Refer Table 4) where the performance
uses various image size (pixels) of grey-scale image.
12
Image Size (pixels)
Image size on disk
Encryption time in ms with AES
Encryption time in ms with Modified AES
256x256 192 KB 6.443 6.349
512x512 257 KB 8.643 8.565
512x512 768 KB 25.256 25.007
1024x1024 2.25 MB 75.862 75.114
Table 4: Performance of AES and Modified AES Encryption
Next, this image encryption technique is based on region and selective part of the image
(refer to Table 5). This encryption is for those who want to encrypt or hide a certain part
of the images. There are few outer step for this encryption. First, select an image that
want to encrypt. Then, choose amount of part in the image or region to encrypt. After
that, an encryption process is executed and private key is being distributed. The user
now acquires an image with regional-encrypted and a key to decrypt the region part of
the image [14]. The model encryption for region based selective image encryption
shown in Figure 3new [15]. This research is based on previous work which working on
image encryption using position permutation technique and value transformation
technique [15-16].
Figure 5: Model Encryption of Region Based Selective
Image Encryption
13
Author Title Description Method
K.C.Ravishankar,
M.G.
Venkateshmury
Region Based
Selective
Image
Encryption
The encryption
technique uses the
selective region in the
image. It will use
transposition
technique
Position permutation
technique, value
transformation and
combine both.
Table 5: Research about Region Based Image Encryption
To see the result or the outcome from this image encryption, refer to the Figure 6.
Only a region in the image are encrypted.
Figure 6: Region-based Encryption Result
For the third image encryption research (refer Table 6), I choose the research conduct
by Aditee Gautam, Meenakshi Panwar and Dr. P. R Gupta. This research is about a
new image encryption using a block based transformation algorithm.
14
Author Title Description Method
Aditee
Gautam,
Meenakshi
Panwar,
Dr.P.R
Gupta
A New Image
Encryption Approach
Using Block Based
Transformation
Algorithm
An encryption
technique using block
cipher by combining a
multiple image in
transformation
Block-cipher
modes, Image
permutation
technique
Table 6: Research about Image Encryption using Block-Cipher
This encryption technique uses a transformation approach where the original image
is divided to a number of block as it is used block based. The block then shuffled
within the image to build a newly transformed image. Which means the encryption
is performed by shuffling the block of pixels in the image. This encryption uses a
secret key approach [17].
Author Title Description Method
Xiang
FeiˈGuo
Xiao-
cong
An Image Encryption
Algorithm based on
Scrambling and
Substitution using
Hybrid Chaotic
Systems
This project simulates an
encryption technique by
scrambling the image
pixel then substitution
technique was applied
after scrambling.
Scrambling
Technique, and
Substitution based
on Chua’s Chaotic
Map
Table 7: Research about Image Encryption with Hybrid Chaotic Systems
And in this research (refer Table 4) it is a bit different with others, it applies a chaotic
system in the encryption technique. This paper use two different chaotic maps that
is why it is a hybrid system. The chaotic maps use is 2-Dimensional Logistic map
and a complicated Chua’s system. The encryption starts with a generation of
15
scrambling matrix by using the 2D Logistic map to generate a chaos sequence and
the length of the generated sequence is respect to the value of MxN (where M is
width and N is height of the image) [18]. After that, a substitution for the pixels is
perform between original pixel and chaotic sequences that generated by the Chua’s
system using Equation (3). This algorithm provides a good confusion and diffusion
where the key space is large and the algorithm also very sensitive to the initial
conditions.
The last one that I chose from most of the research is a paper about Image Encryption
using Advanced Hill Cipher Algorithm as stated in Table 8.
Author Title Description Method
Bibhudendra
Acharya Saroj
Kumar Panigrahy,
SaratKumar Patra,
and Ganapati Panda
Image
Encryption
Using
Advanced Hill
Cipher
Algorithm
This image encryption
uses a novel Advanced
Hill Cipher Algorithm
which can be use both
for greyscale image and
colour-image.
Advanced
Hill Cipher
Algorithm
Table 8: Research about Image Encryption using AdvHill Cipher
This paper proposed an Advanced Hill or (AdvHill) cipher algorithm which uses an
involuntary key matrix for encryption. The objective for this research is to overcome
the drawback of using a random key matrix that happen to be used in Hill Cipher
algorithm for encryption, where it may not be able to decrypt the encrypted message
if the key is not invertible [19]. This encryption works well for greyscale, colour
image, except the one that have background of same grey level.
16
2.4.Summary
This chapter discussed about the implementation of chaos theory and for further
explanation how this image encryption works will be explain in Chapter 3 and
Chapter 4 for this proposed project. A few selected research is discussed throughout
this chapter.
17
Chapter 3:
Methodology
In this chapter, explanation about how the project been develop and what
components and requirement are needed in order to reach the project goals. The
methodology part for this chapter covered the logical schematic how my proposed
project behaves. The theory, method and simple description are demonstrated in this
chapter. Next, this chapter illustrate the flowchart, framework and detailed logical
process how the proposed project looks like.
3.1. Methodology
Figure 7: Project Methodology
Defining Phase Planning Phase Designing Phase
Analysis Phase
Phase Development
Phase
18
The initiative that I had took was using a general project methodology as shown in
Figure 7. This project development took five phase. Which is defining, planning,
designing, development and last one is analysis the project. All those phase have their
own contribution toward this project development. In the next section, are to provide
the general understanding along the project development.
3.2. Defining Phase
Figure 8: Defining Field of Study
In this phase, exposure towards field that I needed and software requirement for
this project. To be exact, this phase only covered the general knowledge regarding to
this project (refer Figure 8). Therefore, subject that are need to be consider are, image
encryption, block cipher, and chaotic map. This is to fulfil the objective of the proposed
project where I created an image encryption using chaotic map (chaotic-based
cryptosystem) in block cipher. For software requirement. This proposed project need a
few software like ImageJ, NetBeans IDE, MATLAB
Field of Study
Image Encryption
Chaotic Map
Block Cipher
Software Requirement
ImageJ: Image Analysis
NetBeans IDE
MATLAB
19
3.2.1. Field of Study
Image encryption is an ability to hide the information or content of the images
by converting the real image (plain-image) into an unreadable image (cipher-image).
This is to protect the confidentiality of the image from any unauthorized users from
reading it. However, in order to read the cipher-image, one need to have a “key” in
order to read the image. So how it works? We will see it in the planning phase and
designing phase.
Chaotic Map is the mathematical function that produce unpredictable trajectories in
graphical interpretation. Usually, this map parameterised by a discrete-time or a
continuous-time parameter. This form of function usually iterated and it often occur in
the study of dynamical systems. Impact from iteration can produce a fractal. Fractal is
a detailed, recursive and infinitely of self-similar mathematical set.
Block Cipher is a method of encryption that applies a pre-determined (deterministic)
algorithm along with distribution of symmetric key to encrypt a block of data. Data can
be in a form of binary or string. Binary data can be obtain from a pixel of image or a
character of string. The block cipher method use a predetermined length of key. The
length of key can be 128, 192 or 256 bits. Block cipher can help to ease the process of
encrypting where the data can be segment into multiple file and encrypt with different
keys.
20
3.2.2. Software Requirement
ImageJ is a standalone software that use to measure the image properties. Image
properties can be in form of RGB colour channel, histogram, and image filtering. This
tool help us to analyse the image encryption from before and after the process. RGB
Colour Channel is a process where we split the encrypted image into three part of filter,
red, green and blue colour channel; this is to ensure that where the encryption takes
place. It also applies for original images. The histogram is an interpretation of images
in graphical concept. This is to show how many pixel represent certain tonal variations
in the image.
NetBeans IDE use to provide an interface image encryption for user to experience the
project that we proposed. Beside, NetBeans also use as a platform to develop this project
from the scratch. The language that going to be carry along the development is Java
language.
MATLAB is a software that use to compute and illustrate a mathematical function. In
this project, we used a chaotic map. Therefore, we used MATLAB to illustrate how the
function behave when we interpret in graphical concept using certain parameters.
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3.3. Planning Phase
In this phase, we start to model a framework that going to be use along the development.
The chaotic-based cryptosystem will receive input from user and process it to produce
an encrypted output with a key. Key that can decrypt the output.
Figure 9: General Overview of Proposed Cryptosystem
Based on Figure 9, situation is John have multiple images that are confidential and need
to send it to Mike. However, they use have two choice to share the image via public
network or share a drive that store the images. The question is, does the sharing session
safe? Then, John came out with the idea to encrypt the images first using a system that
can help to preserve the content of the images from being view by unauthorised person.
So as the system, receive the inputs from John (which are the pictures that he wants
Mike to receive it)
John
Mike
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Then, the cryptosystem will produce outputs. These outputs came in two things. First,
the encrypted-image or cipher-image and a key. Assume that the inputs are three
images. There will be three pair of cipher-images and keys. The purpose of the key is
to unlock (decrypt) the cipher-image. Different key, for different picture.
As Mike received the cipher-image and key, Mike cannot read the image yet. He still
need the cryptosystem to decrypt the cipher-image using the key provided. After
decryption process executed by the system, then Mike will retrieve the real image to see
the content.
3.4. Designing Phase
Designing Phase is a phase where we design a logical concept based on the
framework model in planning phase. The logical concept consists two things in this
proposed project, which are flowchart encryption and decryption.
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3.3.1. Flowchart Encryption
The flowchart encryption demonstrates the logical concept model how the
encryption process happens from the input, to the process and until the output.
Figure 10: Encryption Operation for Proposed Cryptosystem
Figure 10 is a simple representation how the cryptosystem looks like in general
way. The explanation for this logical concept will be demonstrate in detail process.
Processes that take part in encryption operation are:-
a) Input Plain-image and Image Channel Separation
b) Chaos Sequence Key Generation
c) Channel Encryption
d) Image Channel Merger
e) Cipher-image and Key
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3.3.2. Flowchart Decryption
We will go through the steps for encryption logically to get the general understanding
for this purposed project. Before that, let us go through the decryption operation. Refer
to the Figure 11 to see the simple decryption representation.
Figure 11: Decryption Operation for Proposed Cryptosystem
Decryption operation is a reverse operation for encryption. The purpose of this
operation is to retrieve the original image (plain-image) by using two inputs, the
encrypted-image (cipher-image) and the key. These are tasks in the decryption
operation:-
a) Input Cipher-image, Input Key, and Image Channel Separation
b) Reverse Channel Encryption
c) Image Channel Merger and Plain Image
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3.4. Development Phase
In this phase, demonstration of logical concept for this cryptosystem are illustrated. This
phase contains every process throughout the encryption and decryption. First, let see
how encryption process logically using this concept.
3.4.1. Encryption Phase
Figure 12: Input Plain-image and Image Channel Separation
3.4.1.1.Input Plain-image and Image Channel Separation
In this Figure 12, it shows that input image is insert and the image then get into the
image channel separation. In the image separation, split the image into three channel,
red, green and blue channel as shown in Figure 13. The reason we separate the channels
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for the image is that we want to create an encryption for those channel to create “a layers
of scrambling”.
Figure 13: Process for Image Channel Separation
Figure 14: Chaos Sequence Key Generation
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3.4.1.2.Chaos Sequence Key Generation
In the Chaos Sequence Key Generation stage (as shown in Figure 14), an Equation (1)
in the Rossler System will be demonstrated. The purpose application of Rossler System
in this encryption is to generate amount of chaos sequence to create a key. The Equation
(1) in the Figure 15 have a chaotic behaviour based on these initial conditions, where
a= 0.2, b=0.2, and c=5.7
Then we set the initial conditions for x,y and z. Based on 128-bit key that taken from
ASCII form. The sequence will be in a form of K. Where K is denoting the 8-bit key
character. K is the size of 16. That is probably need only 128bits per encryption.
Figure 15: Rossler System’s Equation (1)
Figure 16: Pixels Illustration
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The key provided from this equation will be used throughout the process encryption and
decryption. This encryption will take place from pixel by pixel for an image, consider
x is a row, and y is a column. Then the encryption will be in I(x,y). Figure 16 is an
example illustration of where the encryption happened. The encryption will be on every
pixel of the image, the coordinate for the pixel determined by the value of x and y.
3.4.1.3.Channel Encryption
Figure 17: Channel Encryption
In Digital Image Processing, image is constructed by pixels. Where pixels are made from
combination of primary colour. For this part, we will see about how Red, Green, Blue and Alpha
affect this encryption. This encryption will be demonstrate to every single pixels in four
different channels refer Figure 18 to see preparation of image before encrypt. This encryption
also affect the transparency level for the image (Alpha Channel), the higher the number, and
the more opaque the pixel will be. For further detail on the encryption process will be explain
in the Chapter 4.
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Figure 18: RGB Channel of Lena.png
3.4.1.4.Image Channel Merger
Figure 19: Image Channel Merger
In this Image Channel Merger, the encrypted image for those channels will be merge
again. The post-process for the image will be like Figure 20. The encryption method
will be applied to all three channel this to provide an unpredictable sequence of
encrypted pixels for the image; the outcome should looks like Figure 21.
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Figure 20: Process after Encryption for Different Image Channels
Figure 21: Outcome from Image Merger Operation
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3.4.1.5.Cipher Image and Key
As the process merger complete. User will get two different files, which are the
encrypted images, and the key to decrypt the images. Figure 22, generally tells us the
concept for this cryptosystem.
Figure 22: Overview for Cipher-image and Key Distribution
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3.4.2. Decryption Phase
3.4.2.1.Input Cipher-image, Input Key, and Image Channel Separation
In this process refer Figure 23, the cryptosystem will receive two inputs. Those input
are cipher-image and key. Key that correlated with the cipher-image. Because without
a proper key, it cannot decipher the image. Figure 24 shows an illustration how the
cryptosystem acquired cipher-image, input key. One other thing, this decryption process
is a reverse-form of encryption. Therefore, it will separate the cipher-image to get the
encrypted image in three different channels, red, green and blue. After the process done,
those image with different channels will proceed to Reverse Channel Encryption
process.
Figure 23: Input Cipher-image, Input Key, and Image Channel Separation
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Figure 24: Operation for Image Channel Separation
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3.4.2.2.Reverse Channel Encryption
Figure 25: Reverse Channel Encryption
After uploading the key and encrypted image has been separated into three different
channels (Red, Green, and Blue) with information of Alpha Channel in encrypted
image. Then, the decryption process will be execute where all the channel will be
decrypted using formula explain in the Chapter 4. For general review, refer to Figure
26.
Figure 26: Operation for Reverse Channel Encryption
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You surely do not want to read the image in different channel right? Therefore, these
images will be send to Image Channel Merger process.
3.4.2.3.Image Channel Merger and Plain Image
Figure 27: Image Channel Merger and Plain Image
This image channel merger processes the image by combining the different image
channel and produce a single plain-image. Now user can view and save the plain-image
from the encrypted image. Logical concept for this image channel merger were
illustrated in Figure 28
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Figure 28: Operation for Image Channel Merger and Plain Image
3.5. Analysis Phase
Analysis Phase is phase where the cryptosystem being measure by a few things
that might help in my study on how the cryptosystem response towards inputs. These
are following analysis that would take part in this proposed project.
a) Key Sensitivity Analysis
b) Statistical Analysis (Histogram)
c) Statistical Analysis (Correlation and Coefficient)
d) Fixed Point Analysis
e) Intensity Analysis
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3.5.1. Key Sensitivity Analysis
This analysis is test the reliability of the key in the string value. This is because, the
initial condition for this key generation requires user to input and generate it
automatically. When the initial condition for the image decryption change, it will
produce a different outcome during decryption process.
Figure 29: Key Sensitivity Analysis
As you can observe in Figure 29, the key analysis was performed. If you can see
properly, there is one-bit change at the end of both key. When user tend to alter the key,
the result of decryption cannot produce the plain-image. This shows that this encryption
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is reliable because when a key can be altering even one-bit, that means the encryption
is not secured.
3.5.2. Statistical Analysis (Histogram)
In histogram analysis, it just provides how the image looks like in graphical
interpretation on how the tonal distributed in the image. As you can see in Figure 30 is
a histogram analysis for greyscale picture, the picture of Lena (Figure 1(a) in Figure 30)
representation in histogram can be found in (Figure 1(c) in Figure 30) this to show a
quantity of tonal distribution of the image is stated and it follows the image. But if you
see the “Encrypted Lena” and its histogram. The tonal distributes in a random way
where it cannot be determined.
Figure 30: Statistical Analysis Histogram of Greyscale Image
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Figure 31 is another example but in RGB picture. This encryption took place for these
three different channels. This is why this analysis is studied, because we want to get the
amount of unpredictable for every single pixel in the picture.
Figure 31: Statistical Analysis Histogram of RGB Channel Image
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3.5.3. Statistical Analysis (Correlation and Coefficient)
In this analysis, we going to figure out what happen to the correlation every pixel in the
image. The objective is to ensure that the amount of pixel that still correlated after
encryption is less. That means, the lesser the amount of pixel correlated after encryption,
the better the encryption. As you can see in Figure 32, the pixel somehow still correlated
to one another before encryption. After the decryption process, the correlation between
pixels is uncertainty and complete random.
Figure 32: Statistical Analysis Correlation and Coefficient of the Greyscale Image
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3.5.4. Fixed Point Analysis
The fixed point analysis is an analysis that demonstrate how many pixels that still the
same value, after encryption. In every encryption, the must be one or two pixel that are
still in the same value. Logically this analysis objective is to give a visual interpretation
of how many pixels that are still in the same spot after encryption process.
3.5.5. Intensity Analysis
This analysis is to give a visual how tampering an encrypted image can affect the
decryption process. This analysis conduct with inputs from key from encryption and
image that were used in the encryption process but only the image has been tampered.
Tampered means that partial or region part of the image has been replaced with black
pixel. Figure 33 shows how tampered picture can affect the decryption process.
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Figure 33: Intensity Analysis (Tampered Images as Input)
As you can see, the distorted outcome is measured by how much it has been tampered.
So the image can still be seen if the amount of tampered region is small.
3.6. Summary
Methodology is one of the most important roles in the any project development,
it gives insight generally for people to get our idea for the proposed project. So in this
methodology I choose the methodology that consists, defining phase, planning phase,
designing phase, development and analysis phase. Which I can say that this
methodology help to have a reliable project method. The operation and tasks in this
methodology are explained in order to get understanding for the proposed project.
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Chapter 4
Implementation and Result
4.1. Introduction
In this chapter will provide an insight how the image encryption and decryption
using chaotic-based encryption works. It will measure the encryption and decryption
based on the time taken to complete, the result channel comparison and analysis
histogram. The result will also be shown particularly for encryption process.
4.2. Cryptographic Scheme
Throughout this section 4.2(Cryptographic Scheme), please refer to Figure 34 in order
to understand the encryption and decryption process. In the Figure 34, it shows Pixel
for column 1 and row 1 on the image.
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Figure 34: Pixel (1, 1) Representation for Lena.png
4.2.1. Image Encryption Cryptosystem Scheme
The encryption method use as shown in Formula 1 below. This formula cannot be fully
understand the mechanism, proceed to the Formula 2 to understand the whole
encryption process. 256 in the Formula 1 represent the limit or boundary for the image
encryption. Which the image contain 28 which equals to 256 binary bit weight in
decimal
Encryption = (RosslerSequenceChannel * 256) * (Next Channel –
RosslerSequenceChannel)
Formula 1: General Formula Encryption using Chaotic Based
This encryption process require the image to be split in term of channels. The
channels used in the splitting process are Red, Green, Blue and Alpha and the most
important part is the Rossler Sequence that generate from Rossler Equation (1) that
45
mentioned in Chapter 3.5.1.2. Figure 35 shows a sequence generated from Rossler
Equation (1). This sequence is generated based on how much pixels wants to be
encrypted and the floating point is generated instead of integer numbers. There are four
columns each four can be a sequence in Red, Green, Blue and Alpha channels. Check
on the Formula 2 for implementation of Rossler sequence for each channel for pixel
shown in Figure 34.
Figure 35: Rossler Sequence Generation
Figure 36: Encryption Process for each Channels
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The encryption process will be use the first row of Rossler Sequences in Figure 35 and
the calculation is based on Figure 36. The input variable use in Formula 2 was taken
from Figure 34.
Encrypted Red Channel: (1.0676625 * 256) * (137 - 1.0676625) = 36855
Encrypted Green Channel: (-6.7932353 * 256) * (226 - (-6.7932353)) = -403448
Encrypted Blue Channel: (1.0208428 * 256) * (125 - 1.0208428) = 66033
Encrypted Alpha Channel: (1.01 * 256) * (255 - 1.01) = 31734
Formula 2: Detailed Formula Encryption using Chaotic Based
After the encryption, it will produce the image as shown in the Figure 37. The image
is Lena.png after encryption and demonstrate in term of image channel.
RGB
Red Channel
Green Channel
Blue Channel
Figure 37: Lena.png after Encryption in 3 Different Channels
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4.2.2. Image Decryption Cryptosystem Scheme
In this section we will discuss about how the decryption method being apply in order to
retrieve the original image. The image in Figure 34 will be used in order to retrieve the
original image.
Decryption = EncryptedNextChannel / (RosslerSequenceNextChannel * 256) +
RosslerSequenceNextChannel)
Formula 3: General Formula Decryption using Chaotic Based
Figure 38: Decryption Process for each Channels
What makes this encryption special is that it use the symmetrical keys to encrypt and
decrypt the image. Thus, the channels of the image is bind in pair. Where the red channel
will be bind with green channel of the image and the blue channel will be bind with the
alpha channel of the image. Refer to Figure 38 and Formula 4 for more detail
explanation. Formula 4 used the input based on result from Formula 2.
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Decrypted Red Channel: -403448 / (-6.7932353 * 256) + (-6.7932353)
Decrypted Green Channel: 36855 / (1.0676625 * 256) + (1.0676625)
Decrypted Blue Channel: 31734 / (1.01*256) + (1.01)
Decrypted Alpha Channel: 66033 / (1.0208428 *256) + (1.0208428)
Formula 4: Detailed Formula Decryption using Chaotic Based
RGB
Red Channel
Green Channel
Blue Channel
Figure 39: Lena.png after Decryption in 3 Different Channels
After the formula for decryption process has been done all pixels in the image using the
formula provide in Formula 4. The image channels will be merge and create an image
that has been decrypted.
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4.3.Simulation
For this project, a development of application using NetBeans IDE and Java
Programming were used to create a simulation of how the image encryption and
decryption using the chaotic based. Figures in this section will be divided into two parts,
the encryption process and decryption process.
4.3.1. Encryption Process
The encryption takes place where the user have to upload the image for encryption
process.
Figure 40: Encryption Flow (i) – Menu Interface
The user can only upload image in order to proceed to the next process, which is the
image channel separator. If the file upload is not an image file, further process will not
be execute.
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Figure 41: Encryption Flow (ii) – Upload Image Interface
Figure 42: Encryption Flow (iii) – Preview Image Upload Interface
51
Figure 43: Encryption Flow (iv) – Image Channel Separator Preview Interface
The purpose of image channel separator is to let user see and preview their image, how
does the image look in three different channel (Red, Green and Blue). After user click
on the button next. Encryption process will be done for each pixel using the formula
stated in Chapter 4.2.1.
Figure 44: Encryption Flow (v) – Image Encrypted Interface
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The simulation also timed the encryption process. For Lena.png with the width and
height 512x512pixels. The encryption process take up to 63437056000 nanoseconds
which equivalent to 1.05 minutes. The time taken in nanoseconds, seconds and minutes
are stated in Figure 45.
Figure 45: Encryption Flow (vi) – Time Taken for Encryption Status
As stated in the Flowchart for Encryption in Chapter 3.3.1. The encryption process also
provide three files, the encrypted image and the key to decrypt the image in text file and
the encrypted image in PNG file, refer Figure 46. The process of decryption will be
explain in the next section.
Figure 46: The Encrypted Image and Key for the Image
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4.3.2. Decryption Process
The decryption process will required two things, the encrypted image and the key in
form of text file as shown in Figure 46. The content of those file will look like Figure
47 and Figure 48. Only the text file interpretation can be upload for decryption. The
PNG is not allowed because the reconstruction of pixel requires every single coordinate
store in the text file.
Figure 47: The Content of encryptedimg.txt
Figure 48: The Content of key.txt
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The similarities between these two files are the number of column it had is 4 (represent
the channels Red, Green, Blue and Alpha) and the number of row is equal to the amount
of pixel the image had. Based on Figure 49 and 51, the process of decryption will only
be further when the encrypted image and key is identical and match. If the encrypted
image and key file is recognized, the interface in Figure 51 will open and the image is
ready for decryption process.
Figure 49: Decryption Flow (i) – The Upload Encrypted Image and Key Interface
Figure 50: Decryption Flow (ii) – The File Selection Interface
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Figure 51: Decryption Flow (iii) – Encrypted Image Preview Interface
Figure 52: Decryption Flow (iv) – Image Decrypted Preview Interface
Figure 53: Decryption Flow (v) - Time Taken for Decryption Status
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After click on “Decrypt Image”, the interface of the system shows in Figure 52 with the
time taken for decryption. The decryption process took 54444287574 nanoseconds
which equivalent to 0.9 minutes to decrypt the image. The process seems faster than the
encryption process, this is because the clock speed of the machine, process running also
affect in term of efficiency for the system.
4.4.Result Analysis
There are few analysis were made during and after the image encryption. The analysis
that we mentioned are the Image Channel Analysis and Image Histogram Analysis.
4.4.1. Image Channel Analysis
In image channel analysis, the purpose is to observe how much the encryption affect
the pixels formation in each channel. This analysis can be perform in the simulation
itself (Refer Figure 44) and ImageJ application. For easier explanation, ImageJ were
used to perform the Image Channel Analysis. Choose the encrypted image as shown in
Figure 54.
Figure 54: Folder Contain Files during Process Encryption and Decryption
57
Figure 55: Image Channel Analysis (i) – Image Preview Interface
After open the file, ImageJ will preview the image and amount of pixels the image had.
Go to the menu Image > Color > Split Channels (as shown in Figure 56) to perform
the Image Channel Splitting. The result will be displayed
Figure 56: Image Channel Analysis (ii) – Split Channels Option Interface
58
After the option has been chose, ImageJ will execute the channel splitting process. The
result can be seen in Figure 57.
RGB Channel for Encrypted
Lena.png
Red Channel for Encrypted
Lena.png
Green Channel for
Encrypted Lena.png
Blue Channel for Encrypted
Lena.png
Figure 57: Image Channel Analysis (iii) – RGB Channels Preview for the Encrypted
Lena.png
4.4.2. Image Histogram Analysis
Image Histogram Analysis is a practice to study the context of the image via pixel
density value of the image. It plot the pixel density for each tonal value. For example,
in Figure 58 shows that the Histogram for Red, Green, and Blue image after Image
Separation of random image (this is not Lena.png’s Histogram Analysis). The pixel
intensity is measure by how many pixel frequency appeared in the image itself.
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Figure 58: Image Histogram Analysis (i) – Example Histogram Analysis.
The process for this analysis will required a software called MATLAB. MATLAB
enable us to convert the image into a histogram interpretation. But, MATLAB only
produce the histogram for grayscale image and histogram for red, green and blue
channel separately. In this analysis, two image were used Lena.png and Encrypted
Lena.png as shown in Figure 59.
Lena.png (512x512 pixels)
Encrypted Lena.png (512x512 pixels)
Figure 59: Image Histogram Analysis (ii) – Inputs for Histogram Analysis
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There are two Image Histogram Analysis been perform for this image. The analysis
shows that there are no similarities between two images in Figure 59. The grayscale
histogram analysis for these image can be seen in Figure 60 and Figure 62. Figure 61
and Figure 63 shows the execution code to perform Histogram Analysis in MATLAB.
Figure 60: Image Histogram Analysis (iii) – Grayscale Histogram for Lena.png
Figure 61: Image Histogram Analysis (iv) – Extract Histogram Lena.png in MATLAB
Figure 62: Image Histogram Analysis (v) – Grayscale Histogram for Encrypted
Lena.png
61
As you can see the pixel density and frequency does not match between before and after
encryption of the image. This is a good practice where the intruder or anyone cannot
have a precise guess on how the image looks like.
Figure 63: Image Histogram Analysis (vi) – Extract Encrypted Lena.png in MATLAB
Next, a demonstration for Histogram Analysis for each channels in the image (Red,
Green and Blue). This is the part where the image will be separate to each channel,
MATLAB then produce the histogram and merge all three channel into one histogram.
Each colour represent each channel in the image. Figure 64 and 67 shows the histogram
analysis.
Figure 64: Image Histogram Analysis (vii) – RGB Histogram Representation
Lena.png
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Figure 65: Image Histogram Analysis (viii) – Extracting Lena.png in MATLAB
Figure 66: Image Histogram Analysis (ix) – RGB Histogram Representation
Encrypted Lena.png
Figure 67: Image Histogram Analysis (x) – Extracting Encrypted Lena.png in
MATLAB
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Chapter 5
Conclusion
5.1. Summary
Image Encryption is an art of scrambling, transposing, or even altering the pixel value
of the image in order to secure the content of the image. This is an important field to
practice and do a research on how to provide a reliable security services in terms of data
exchange. Because nowadays, people have many private and personal image data that
being kept locally and virtually (using Cloud Storage). This is a good opportunity to
emphasize the cryptography implementation in any kind of data.
Furthermore, cryptography is a study to provide a security in protect data integrity from
being compromised to other parties by kept the data secret (encryption) and provide a
key (public key or private key). Where they key is the solution to decipher the encrypted
data and view the original data (decryption). In this project, where combining the
chaotic-based cryptosystem, every single pixels from the image channels are being
transpose into other pixel. Where the encrypted pixels can only be decrypt using the
only key (private key) provide during encryption.
This research focus on the study of image encryption using chaotic based cryptosystem
to ensure the integrity and availability of image data during data exchange. In this
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research, the chaotic system that been implement is Rossler Equation (I) where I use
the Rossler Sequence to generate numbers to be use as variable to encrypt each channels
for the image (refer Chapter 4.2) for more explanation. It is a small contribution towards
creating a new environment of safe image data exchange in the network.
For future work, I hope someone who have genuine interest and passion to continue this
research and improve any weakness that might be find technically or logically.
Implementing chaotic cryptosystem with public key infrastructure would be a great
combination.
To conclude, I have already fulfilled all the objective and tasks I have propose earlier
in the developing this project. This issue in encrypting image to have secure data
exchange environment does not ends here. There are probably a way to tackle the
problem, where people need a new secure environment in an open network to share
their own data to their own particular people.
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