International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 5 – Jul 2014
A Novel Text to Image Encryption Technique by
AES Rijndael Algorithm with Color Code
Conversion
Shanthi1
Dr.V.Palanisamy2
M.Phil Research Scholar
Department of Comp.Sci & Engg
Alagappa University
Karaikudi .
Abstract - Transmission of secure data through the
communication spectrum is major issue in current scenario. To
ensure the security of the data, many techniques and algorithms
were evolved in which the cryptographic techniques are most
powerful. Through cryptographic algorithms, the conversion of
plain text into unintelligible form made it more secure and
protect data from unauthorized users. The proposed scheme
focus on the block cipher substitution method that encrypts the
given text into blocks. In this paper, our proposed method
extends such that, the user given plain text is divided into blocks
that are fed to the AES Rijndael encryption process, converted to
unreadable format. Each character of the block is then shifted
into ASCII value which is, in turn formulated into equivalent
color code. Thus, the final encrypted text is in image format
which make available for more enrichment to the data. The AES
algorithm is chosen for its quick and legible conversion of data.
Our proposed method is very flexible technology for 256 ASCII
values that is converted into 256 color code.
Keywords- Block cipher, Cryptography, Encryption, Decryption,
Color Substitution, AES Rijndael Algorithm.
I. INTRODUCTION
Cryptography is the science of information security.
Cryptography includes techniques such as microdots, merging
words with images, and other ways to hide information in
storage scenario. However, in today's computer-centric world,
cryptography is most often associated with scrambling
plaintext (ordinary text, sometimes referred to as clear text)
into cipher text (a process called encryption), then back again
(known as decryption). Individuals who practice this field are
known as cryptographers. Key is used to authenticate purpose.
With the help of key sender make sure correct receiver would
decrypt the message [11].
In wireless networks, the security of data is an
important aspect and
encryption algorithms play an
important role to provide the security to the wireless
networks. The main aim of the cryptography is to
enhance the data confidentiality and privacy by making
the information unintelligible. Hence the data cannot be
interrupted by the intruders. The Encryption techniques and
various algorithms are used to provide the needed security to
the applications [3].
The rapid growth of computer networks allowed large files,
such as digital images, to be easily transmitted over the
internet [10,1]. Data encryption is widely used to ensure
security however, most of the available encryption algorithms
ISSN: 2231-5381
Professor
Department of comp.sci & Engg
Alagappa University
Karaikudi
are used for text data. Due to large data size and real time
Constrains, algorithms that are good for textual data may not
be suitable for multimedia data [10, 2, and 4].
The type of operations used for transforming plaintext to
cipher text: all the encryption algorithms are based on two
general principles: Substitution, in this each element in the
plaintext (bit, letter, group of bits are letters) is mapped into
another element and the transposition in which elements in the
plain text are rearranged. Most systems, referred to as product
systems, involve multiple stages of substitution and
transposition [6].
A block cipher processes the input into multiple blocks and
proceeds each block of elements at a time, producing an
output block for each input block. A stream cipher processes
the input elements continuously, producing output one
element at a time, as it goes along [3].
Basically, the encryption technique is divided into two
types namely the Symmetric Key Encryption and Asymmetric
Key Encryption. Encryption in Symmetric-key schemes, the
encryption and decryption keys are the same. Thus
communicating parties must agree on a secret key before they
wish to communicate [11].
In public-key encryption schemes, the encryption key is
published for anyone to use and encrypt messages. However,
only the receiving party has access to the decryption key and
is capable of reading the encrypted messages. Public-key
encryption is a relatively recent invention historically; all
encryption schemes have been symmetric-key (also called
private-key) schemes. Cryptanalysis is the process of
deciphering coded messages without being told the key.
Cryptanalysis refers to the study of ciphers, cipher text, or
cryptosystems (that is, to secret code systems) with a view to
finding weaknesses in them that will permit retrieval of the
plaintext from the cipher text, without necessarily knowing
the key or the algorithm. This is known as breaking the cipher,
cipher text or cryptosystem [11].
The rest of the paper is organized as follows. Section 2
come out with various works related to text to image
encryption methodology. Section 3 consists of various
algorithms that are used for encryption technique. Section 4 is
the proposed work, along with models and examples. Section
5 comes with experimental results concludes the proposed
work.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 5 – Jul 2014
II. RELATED WORK
Ahmad Abusukhon, Mohammad Talib and Maher A.
Nabulsi in their paper, have shown the efficiency of the text
to image encryption algorithm analyses. Abusukhon and
Talib [1] proposed a novel data encryption algorithm
called Text-to-Image Encryption algorithm (TTIE) in
which a given text is encrypted into an image. Each
letter from the plaintext is encrypted into one pixel [2].
Sourabh Singh,, Anurag Jain, shown An Enhanced Text to
Image Encryption Technique using RGB Substitution and
AES algorithm. Under this approach, the secret key is
smartly sent along with the cipher text in a single transmission,
thus it also solves the key exchange problem that generally
arises in most of the encryption models. The encryption and
decryption process make the use of a combination database
for text to image transformation [10].
Komal D Patel, Sonal Belani, proposes a survey on various
existing techniques for image encryption, their advantages and
working methodologies[5].Mohammad Ali Bani Younes
and Aman introduce a block-based transformation algorithm
based on the combination of image transformation and a well
known encryption and decryption algorithm called
Blowfish. The original image was divided into blocks, which
were rearranged into a transformed image using a
transformation algorithm, and then the transformed image
was encrypted using the Blowfish algorithm. Their results
showed that the correlation between image elements was
significantly decreased [7].
Singh and Gilhorta [9] proposed encrypting a word of
text to a floating point number that lies in range from 0 to 1.
The floating point number is then converted into binary
number and after that one time key is used to encrypt this
binary number. In tht work, they encode each character by one
pixel (three integer values R, G and B).
K. Ravindra Babu, Dr .S.Udaya Kumar, Dr. A.Vinaya
Babu,and Dr. Thirupathi Reddy, extends their views ona
block cipher generation using color substitution method. From
their work, they conclude that, the new algorithm given by
them for the color substitution method is good and potential
one against the brute force attack. Moreover, analytically the
results are formulated [8].
Jawad Ahmad and Fawad Ahmed have compared two
encryption algorithms namely
Advanced
Encryption
Standard (AES) and Compression Friendly
Encryption
Scheme (CFES). They have explored the security estimations
of AES and CFES for digital images against brute-force,
statistical, and differential attacks, the results they have
calculated to test the security of these algorithms for digital
images shows some weaknesses in CFES. These weaknesses
were mainly related to low entropy and horizontal correlation
in encrypted images. The algorithm which has less correlation
values indicates that it has higher security [4].
The security of digital images has become more and more
important due to the rapid evolution of the Internet in
the digital world today. The security of digital images has
attracted more attention recently, and many different image
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encryption methods have been proposed to enhance the
security of these images [9].
The most influential and universal approach to countering
the threats to network / information security is encryption.
Even though it is very authoritative, the cryptanalysts are very
intelligent and they were working day and night to break the
ciphers. To make a stronger cipher it is recommended that to
use: More stronger and complicated encryption algorithms,
Keys with more number of bits (Longer keys), larger block
size as input to process, use authentication and confidentiality
and secure transmission of keys.
III. EXISTING TECHNIQUES
For the cryptographic process there exist many algorithms
and methods. This section briefly discuss on the substitution
method encryption and decryption procedure. The algorithms
such as symmetric key encryption also explained in the
following section:
A. Symmetric Key Encryption
The most important type of the encryption type is the
symmetric key encryption. In the symmetric key encryption
both for the encryption and decryption process the same key is
used. Hence the secrecy of the key is maintained and it is kept
private. Symmetric algorithms have the advantage of not
consuming too much of computing power and it works with
high speed in encryption.
A block cipher is taken as the input, a key and then the
output block will be same in size in the symmetric key
encryption. The symmetric key encryption takes place in two
modes either as the block ciphers or as the stream ciphers. In
the block cipher mode the whole data is divided into number of
blocks and based on the block length the key is provided for
encryption.
B. Substitution Algorithm
There exists two form of encryption namely the
substitution and the transposition. In the substitution method
one character will be exchanged for the character, and vice
versa at the decryption end. The substitution algorithm may be
in many formats such as the monoalphabetic substitution,
polyalphabetic substitution, vigenere cipher, playfair cipher
etc.,
In a monoalphabetic cipher, the same substitution rule
is used at every character position in the plaintext message. In
a polyalphabetic cipher, on the other hand, the substitution rule
changes continuously from one character position to the next in
the plaintext according to the elements of the encryption key.
The block substitution table has the following function, and
this is the earliest known example of a substitution cipher.
• Each character of a message is replaced by a
character three position down in the alphabet.
plaintext: are you ready
ciphertext: DUH BRX UHDGB
• If we represent each letter of the alphabet by an
integer that corresponds to its position in the alphabet, the
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 5 – Jul 2014
formula for replacing each character p of the plaintext with a
character c of the cipher text can be expressed as
c = E (3, p) = (p + 3) mod 26
where E () stands for encryption. If you are not already familiar
with modulo division, the mod operator returns the integer
remainder of the division when p + 3 is divided by 26, the
number of letters in the English alphabet. We are obviously
assuming case-insensitive encoding with the Caesar cipher.
C. AESRijndael Encryption Algorithm
The encryption algorithm is an integral work of image
encryption and decryption process. They should preserve high
security to the image transmitted. Basically, encryption
algorithms are divided into three major categories –
transposition, substitution, and transposition – substitution
technique. The AES Rijndael algorithm is the advanced
encryption standard algorithm, used most widely for
encryption because of its simplicity and efficient working
syntax. Rijndael is an iterated block cipher at with a variable
block length and a variable key length. The block length and
key length can be independently specified to 128,192 or 256
bits. Internally the AES algorithm’s operations are
performed on a two dimensional array of bytes called the
state. The state consists of four rows of each bytes, each
contains Nb number of bytes, where Nb is the block length
divided by 32. The function involved in AES algorithm is, sub
bytes transformation, Shift rows Transformation, Mix column
Transformation and Add round key transformation.
IV. THE PROPOSED ALGORITHM AND EXAMPLE
The main intention of this paper is to present an innovative
cryptographic Substitution method, can generate stronger
cipher then the existing substitution algorithms. We are sure
that concept is new and the cryptanalysis did on this will prove
that the cipher is strong.
A. Proposed Algorithm
The proposed algorithm works as follows:
Step1: Read the input text that is to be encrypted.
Step 2: The input text is encrypted using the AES Rijndael
encryption algorithm and the output is obtained.
Step 3: Now, the encrypted unreadable format is divided
into block ciphers of length 3 characters per block.
Step 4: The block is replaced with 3 color codes R, G, B
respectively for each pixel within the block.
Step 5: The entire known pixel contain 3 components like
Red, Green and Blue. The magic of our algorithm 3
components range between 0 to 255 simultaneously ASCII
table also contain 0 to 255.
The procedure for the, the block substitution is as follows.
Since, in RGB color image systems, a color is typically
represented by three component intensities such as blue, green
and red, then read the given encrypted text and separated it
three characters. Combine the three characters and consider it
as a block. After the separation into blocks, convert it into
corresponding color code, so we can get a single pixel. The
above process repeated until full plaintext is converted to
pixels. This pixel is used to draw a 512 X 512 image.
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As a first step draw row wise 512 pixels once. Until the
final row of the block is reached continuously draw the pixels.
Finally the input text is converted into unintelligible form
image. This is also one of the substitution methods. Here we
are substitute text into pixel. The strength of proposed
algorithm includes rich character set compare to Caesar cipher.
The strength of the algorithm lies in that format that is the user
provided input text is converted into image format.
Fig 1. Block Diagram of Encryption technique with color code
An Example:
welcome – 119,101,108,99,111,109,101
convert into block cipher , 3 characters per block
119,101,108 - RGB (119,101,108) =
99,111,109 - RGB (99,111,109) =
101, 0, 0
- RGB (101,0,0)
=
The step by step process of text encrypted into image and
decrypted the image into text file.
B. Encryption Algorithm
Happy Birthday = Hap py Bir thd ay.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 5 – Jul 2014
D. Advantages of Proposed Method

Step 1: Read each block and get the equivalent ASCII
value.


Hap = 72, 97,112


py = 112,121,32
Bir = 66,105,114
thd = 116,104,100
ay = 97,121,0 Consider each block as pixel. In a
block consider first value as Red, second value as
Green and third value as Blue.
 Step 4: Write it as an image.
C. Decryption Algorithm

Step 1: Read the encrypted image and get the first
pixel.

Step 2: Read each pixel.

Example : First pixel have
A simple and effective algorithm with efficient
working syntax.
It does not need any key for an encryption and
decryption.
It supports 256 characters.
Text is encrypted with the AES Rijndael algorithm;
into image it is so hard to find the plain text.
E. Conversion of plain text to cipher text using the proposed
Method.
The following is the example plain text to cipher text for
different block size and pixel values.
Input Text:
The most influential and universal approach to
countering the threats to network / information security is
encryption. Our proposed work is to present an innovative
cryptographic Substitution method, can generate stronger
cipher then the existing substitution algorithms. We are
sure that concept is new and the cryptanalysis did on this
will prove that the cipher is strong. The substitution cipher
one of the classical ciphers in cryptography. In this method
each letter in the plaintext is replaced by a letter shifted a
fixed number of places to the right. But the existing
methods only 26 alphabets, keys used.
Red = 72, Green = 97, Blue = 112
Encryption Using AES Rijndael Algorithm:
72 = H, 97 = a, 112 = p

Second Pixel.
Red = 112, Green = 112, Blue = (Space) 32
32 = p, 112 = y, 32 = (Space)

Third Pixel.
Red = 66, Green = 105, Blue = 114
66 = B, 105 = i , 114 = r

Fourth Pixel.
Red = 116, Green = 104, Blue = 100
116 = t, 104= h, 100 = d
Red = 97, Green = 121, Blue = 0
97 = a, 121 =y, 0 = NULL
To combine all the characters we get our original
plain text “Happy Birthday”
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cbzxj/g1rMLUk97OvxVN1GxytChm85q+COFbw50
Qi59+sLzQQRrLUsfb6QRZj0zkeh4QBnmmflKhZZtnEojc
0rwF4Gmy9d1+5F+/prbHrvLJWwcwvccYxbILeeFPMdd2
kuQfPgOUVvODmwibifA0eyyFlPDUiqDTWgvX8jIrYpP
87jP5Cyic7U4nRO3eLTrqa2G+R4bZsDJfQQIUG6+f8du
VTtxQb4p5hPYtGdYAo2EFWpxepgbB/rSlo5K6O2c1nW
uNfC4za453Vkuyqa6jz2hwd/xv1oKvN++P7HcK4yiVLqv
GeKbpTbgtt4YZpL04y6MYQxgRC78FpIe+/NWM7zKPb
qrCiRZ8EvA/SSt09O6onXafEuHFssPtl4u/jSULqGPuMT
Umgfh2Vn/MH2EPklvz3Woid+JvHzE/NKTP1+qgIttL2Z
WoIgPX1VLX6FwtJrMlk+zVPApbtl/cnkUd0wHUe93HT
wVdkNjna/cP4f2WvLyoWKDVUq9yH7Llun9UxWentYm
qAZaxM5JzwOUhm7deG87NQPhtSi2jUEnlh33e79g12nH
kDtZUZYLxhfv6OW1dRhgTEyCFz7OJxTnOMwCojyLw
D15QfyHKIs0E9B5EUQvkOzVguBT03RW1QDlT5uw/L
oiot+8Uj/zjNY4Alww8PY8ucQZtA/lYH4NPNmSD7tkAK
4isAYBt5lXycTx0NAW1aO77wsi3KiILI22M6SOHN0bW
MP36sSpFiEbliagdSjRh4W0ydP0I1E2ulr2LmclRuZHPFn
pENQ5XY5QBP1j9+b98YkBCpdtDTlNZ89dcls/Ak8tuX4
rrB7L7UCuNSv96mmGj0lgEU1GI3i0Hrl0kdmWiunNcHF
+OIpSAVEYHgb+8EeKVbBEladaYQzg8gPesXcVS23rA
T3JASRqh+uVsjwIcGaTzHM41oWe7CMxy+hUB/XRC5
FSouyilKv4Wrqhhcmbgxl+JLdZVLEYUolG8m4d/xSlGZ
79Uh13w1RX+YLpDnyNnN2JRyYhxRWP/
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[6] Manoj Kumar, “Cryptography & Network Security”, 3rd ed.,
Krishna Prakashan Media (P) Ltd, 2008.
[7] Mohammad Ali Bani Younes and Aman Jantan “Image Encryption
Using Block-Based Transformation Algorithm”, inIAENG
International Journal of Computer Science, 35,2008.
[8] K. Ravindra Babu, Dr .S.Udaya Kumar, Dr. A.Vinaya Babu,and
Dr. Thirupathi Reddy, “A Block Cipher Generation Using Color
substitution”, inInternational Journal of Computer Applications,
vol1, issue 28, pp:25-29.
[9] Singh, A., Gilhorta, R.:,”Data security using private
key
encryption
system
based
on arithmetic
coding”,in.
International Journal of Network Security and its a (IJNSA),
3(3) (2011).
[10] Sourabh Singh and Anurag jain , in “An Enhanced Text to Image
Encryption Technique using RGB Substitution and AES”, in
International Journal of Engineering Trends and Technology
(IJETT) - Volume4Issue5- May 2013, pp:2108 – 2112.
[11] William Stallings, “Cryptography and Network Security”,
Principles and practice, 5th ed., 2008.
Encrypted Data to Image Conversion
Fig 2. Text to Image Conversion
F. Output Text after Decryption:
The most influential and universal approach to
countering the threats to network / information security is
encryption. Our proposed work is to present an innovative
cryptographic Substitution method, can generate stronger
cipher then the existing substitution algorithms. We are
sure that concept is new and the cryptanalysis did on this
will prove that the cipher is strong. The substitution cipher
one of the classical ciphers in cryptography. In this method
each letter in the plaintext is replaced by a letter shifted a
fixed number of places to the right. But the existing
methods only 26 alphabets, keys used.
V. CONCLUSION
Most of the encryption technique does not woks in
cross platform manner. Here we convert the text into image
this supports cross platform. So, when comparing with other
block cipher algorithm, our proposed algorithm remains
very strong in encryption and in decryption. Complex
computational were also excluded by using this procedure.
So it leftovers fast when compare with the other algorithm.
The Intermediate form is the AES encryption technique,
which increases more security to the data, and since the
divided block is converted to color code, it seems more
complex to the intruders to find out the original text.
REFERENCES
[1] A.Abusukhon, and M. Talib, "A Novel network security algorithm
based on Private Key Encryption". In Proceeding of The
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and Digital Forensic (CyberSec12), 2012.
[2] Ahmad Abusukhon, Mohammad Talib and Maher A. Nabulsi,
“Analysing the efficiency of Text to image encryption algorithm” ,
in International Journal of Advanced Computer Science and
Applications, Vol. 3, No. 11, 2012, pp-35 – 38.
[3] Behrouz A. Forouzan, “Cryptography and Network Security”,
Tata McGraw-Hill, 2007.
[4] Jawad Ahmad and Fawad Ahmed “Efficiency Analysis and
Security Evaluation of Image Encryption Schemes” ,in
International Journal of Video & Image Processing and Network
Security IJVIPNS-IJENS Vol:12 No:04.
[5] Komal D.Patel and Sonal Belani,” Image Encryption Using
Different Techniques:A Review”, in International Journal of
Emerging Technology and Advanced engineering, Volume 1, Issue
1, November 2011, pp: 30- 34.
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