1. IJRREST
INTERNATIONAL JOURNAL OF RESEARCH REVIEW IN ENGINEERING SCIENCE & TECHNOLOGY
(ISSN 2278–6643)
VOLUME-2, ISSUE-2, JUNE-2013
IJRREST, ijrrest.org 68 | P a g e
Implementation of Dynamic Hill Cipher with
Message Digest Concatenation
Encryption Technique in Cloud Computing
*Muskaan Gupta, **Zatin Gupta , ***Ashish Gupta
Abstract— The data security in cloud computing is the core problem. Single security method cannot solve the security problem in
cloud computing. To advance cloud computing measures to ensure security is important. The solution is the data encryption. Before
storing it at virtual location, encrypt the data with keys. User selects the public key to encrypt data and upload the encrypted data to
the cloud. This Paper introduces a strong cryptography algorithm that provides the security of the data in cloud computing. The
proposed algorithm is based on encryption algorithm the hill cipher which was analyzed to be easily breakable if the matrix is known
due to its short key length and does not provide any message integrity. So there is the need to make it more typical for the intruder to
break it. To make data secure we implement a new security system using the strong secured algorithm Dynamic Hill Cipher With
Message Digest Concatenation which ensure message authentication, confidentiality and integrity of the data. Confidentiality provides
protection of transmitted data from passive attacks. The authentication service assures that a communication is authentic. The data
integrity is the assurance that data contain no modification.
Keywords: Cryptography, MD5, Digital signature, Hill cipher technique, Plain texts, Cipher text, ID.
——————————  ——————————
1 INTRODUCTION
loud computing, a rapidly developing information
technology, has aroused the concern of the whole
world. Cloud computing is Internet-based computing,
whereby shared resources, software and information, are
provided to computers and devices on-demand [3]. Cloud
computing is the product of the fusion of traditional
computing technology and network technology like grid
computing, distributed computing, parallel computing and
so on. However, there still exist many problems in cloud
computing today, a recent survey shows that data security
and privacy risks have become the primary concern for
people to shift to cloud computing. To advance cloud
computing, measures to ensure security is important.
Traditionally information security was provided by physical
(for e.g. rugged filing cabinets with locks) and
administrative mechanisms (for e.g. Personnel screening
procedures during hiring process).Growing computer use
implies a need for automated tools for protecting files and
other information stored on it. This is especially the case for
a shared system, such as a time-sharing system, and even
more so for systems that can be accessed over a public
telephone network, data network, or the Internet.
Information security requirements have changed in recent
times. Computer use requires automated tools to protect
files and other stored information. Use of networks and
communications links requires measures to protect data
during transmission. In the new world of computers and
electronics the electronic communication plays a vital role.
There is the basic need for security of data. Security is the
term that comes into the picture when some important or
sensitive information must be protect from an unauthorized
access. Hence there must be some way to protect the data
from them and even if he hack the information, he should
not be able to understand what the actual information in the
file is. It is essential to protect the sensitive information.
There are many chances that an unauthorized person can
have an access over the information in some way and can
access this sensitive information. There are many attackers
who can still break the code to find the message. These data
are important which when in wrong hands can create a lot
of damage to the company. To protect these damages we
need some method to protect our data. Cryptography is
used to protect data from these damages. There is no doubt
that the cloud computing is the development trend in the
future. Cloud computing brings us the approximately
infinite computing capability, good scalability ,service on-
demand and so on, also challenges at security, privacy, legal
issues and so on. With the fast development and widespread
applications of cloud computing, the management and
security of the network virtual access become increasingly
important. To assure security of data from any change done
by the intruder, we implement a new security system using
the strong secured algorithm-DYNAMIC HILL CIPHER
WITH MESSAGE DIGEST CONCATENATION that enables
and guarantees the security of the information. The
proposed system provides the facility to the receiver that
message is same as sent by the sender otherwise if a change
is done then the message will not be received by receiver.
The system is based on encryption and decryption, so it also
facilitates data confidentiality. Only the authorized users of
the system can send and receive the messages. The system
provides message authentication, confidentiality and
integrity of the data which are the necessary requirements
for secure electronic communication between sender and
receiver.
C
____________________________________
*M.Tech Scholar, RPIIT, Karnal, Haryana, India,
Muskaan.gupta31@gmail.com
**Assistant Professor, RKGIT, Ghaziabad, UP, India,
zatin.gupta2000@gmail.com
*** Assistant Professor, RPIIT, Karnal, Haryana, India,
mtech.ashish@yahoo.in

2. IJRREST
INTERNATIONAL JOURNAL OF RESEARCH REVIEW IN ENGINEERING SCIENCE & TECHNOLOGY
(ISSN 2278–6643)
VOLUME-2, ISSUE-2, JUNE-2013
IJRREST, ijrrest.org 69 | P a g e
2 THEORETICAL BACKGROUND
ENCRYPTION
Encryption is a procedure that involves a mathematical
transformation of information into scrambled information,
called “cipher text”. The computational process (an
algorithm) uses a key to compute or convert plain text into
cipher text with numbers or strings of characters. The
resulting encrypted text is decipherable only by the holder
of the corresponding key. This deciphering process is also
called decryption. There are many different and
incompatible encryption techniques available, and not all
the software we need to use implements a common
approach. One very important feature of a good encryption
scheme is the ability to specify a key or password of some
kind, and have the encryption method alter itself such that
each key or password produces a different encrypted
output, which requires a unique ‘key’ or ‘password’ to
decrypt. We are using symmetric block cipher which works
as follows:
`
Figure 1: Symmetric Encryption
The Hill Cipher was developed by Lester Hill in 1929. The
encryption algorithm takes m successive plaintext letters
and substitutes for them m cipher text letters. The
substitution is determined by m-linear equations in which
each character is assigned a numerical value (a = 0, b = 1 ... z
= 25). For m= 3, the system can be described as follows:
c1 = (k11P1 + k12P2 +k13P3) mod 26
c2 = (k21P1 +k22P2 + k23P3) mod 26
c3 = (k31P1 + k32P2 +k33P3) mod 26
This can be expressed as : C = KP mod 26where C and P are
column vectors of length 3, representing the plaintext and
cipher text, and K is a 3 x 3 matrix, representing the
encryption key. Operations are performed mod 26.
Decryption requires using the inverse of the matrix K. The
inverse K-1of a matrix K is defined by the equation KK-1=
K-1 K = I, where I is the matrix that is all zeros except for
ones along the main diagonal from upper left to lower right.
The inverse of a matrix does not always exist, but when it
does, it satisfies the preceding equation.
MD5 (Message Digest 5) Ron Rivest, who has been
designed this algorithm in 1991 to replace an earlier hash
function, MD4 (Message-digest protocol 4). It is a widely
used algorithm in cryptography and often used to check the
integrity of a file. An MD5 hash is typically expressed as a 32
digit hexadecimal number. MD5 processes a variable-length
message into a fixed-length output of 128 bits. The input
message is broken up into chunks of 512-bit blocks (sixteen
32- bit little endian integers); the message is padded so that
its length is divisible by 512. The padding works as follows:
first a single bit, 1, is appended to the end of the message.
This is followed by as many zeros as are required to bring
the length of the message up to 64 bits less than a multiple of
512. The remaining bits are filled up with a 64-bit integer
representing the length of the original message, in bits. The
main MD5 algorithm operates on a 128-bit state, divided
into four 32-bit words, denoted A, B, C and D. These are
initialized to certain fixed constants. The main algorithm
then operates on each 512-bit message block in turn, each
block modifying the state. The 128- bit (16-byte) MD5 hashes
(also termed message digests) are typically represented as a
sequence of 32 hexadecimal digits.
3 PROPOSED METHODOLOGY
Our proposed secured electronic transaction methodology is
dynamic hill cipher and message digest concatenation.
Now here we try to use the concept of dynamic key size that
will be selected by the user one who encrypts the message.
Any security system performs the fundamental security
services: confidentiality, authentication, integrity checking
and non repudiation. The proposed methodology performs
all the security operations and is given in table.
Systems Confidentiality Authentication Integrity
Message
authentica
tion with
encryption
Yes Yes No
Message
authentica
tion with
message
digest
no Yes Yes
Proposed
system
yes yes Yes
Table 1: Comparative analysis for different message
transaction

3. IJRREST
INTERNATIONAL JOURNAL OF RESEARCH REVIEW IN ENGINEERING SCIENCE & TECHNOLOGY
(ISSN 2278–6643)
VOLUME-2, ISSUE-2, JUNE-2013
IJRREST, ijrrest.org 70 | P a g e
3.1 ALGORITHMIC APPROACHES
The algorithm has been divided into two phases. In the 1st
phase, Sender Generates the message to send through some
steps of encryption and in the 2nd phase the receiver
receives the message and decrypt with some methods. The
authentication process is done in the receiver end, if the
authentication is done properly then the message is
displayed or else it is damaged or dropped.
Figure 2: Flow Diagram
The complete algorithm is given below:
Phase - 1: (Sender Site)
1. The sender selects a key length that is used as the length
of the key matrix.
2. Generate a square matrix (M) of length K which has an
inverse matrix (M-1) with the property that the product of
the key matrix and the inverse matrix with modulo
operation produces identity matrix (I). That is, M x M-1 = I.
The matrix M is used as the K in the encryption process and
the inverse matrix M-1 is sent to the destination to use for
decryption.
3. Enter the transmitting message (P) and perform Hill
cipher encryption technique to produce cipher text (C).That
is, C = EK (P).
4. To generate message digest (D), performs the bit-wise
XOR operation in the equal two halves of the message P.
Then again perform the bit-wise XOR operation in the equal
halves of the produced previous output and again perform
the same operation in the last output and final output is the
digest D.
5. The generated message digest D is concatenated to the
cipher text (C) and is sent to the destination B
Phase - 2: (Receiver Site)
6. In the destination, receiver B first decrypts the cipher text
C using the received inverse matrix M-1 and the decryption
algorithm Hill Cipher method to produce the plaintext P.
7. Receiver B then performs the same operations bit-wise
XOR on the plaintext and calculates new message digest
MD’ and compare it with the received message digest MD
and determine the integrity of the message
4 IMPLEMENTATION
The proposed electronic message transaction system has
been implemented using java programming.
 The login interface is in form of textboxes and buttons
where the user has to fill up the user id and password. If
the user is authorized, then only he or she can access the
software.
 After the login window, a new window is designed that
tells how the software works by giving directions. This
window also has three options. These are encryption,
decryption and exit.
 There is an encryption button.
 On click of encryptions button, several other buttons and
two editors will be shown. One of the editors is for writing
or getting of plain text and other is for getting of
encrypted data.
 The various buttons are generate_key, reset_data, encrypt,
save_encrypted_text, back, exit, check_key_validity and
open_file.
 There is a decryption button. On click of this button,
several other buttons and two editors will be shown. One
of the editors is for getting of encrypted text and other is
for gettingof plain text.
 The various buttons are get_data, reset_data, decrypt,
save_encrypted_text, back and exit.
 On clicking of back button, three options again will
reappear. These options are encryption, decryption and
exit.

4. IJRREST
INTERNATIONAL JOURNAL OF RESEARCH REVIEW IN ENGINEERING SCIENCE & TECHNOLOGY
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VOLUME-2, ISSUE-2, JUNE-2013
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Figure 3: ENCRYPTION WINDOW
Figure 4: ENTERING THE KEY SIZE
Figure 5: PLAIN TEXT AND ENCRYPTED TEXT
Figure 6: PLAIN TEXT FROM ENCRYPTED TEXT
5 FUTURE SCOPE
The main achievement is the correctly functional tool itself.
Unfortunately time constraints have meant that not all the
originally mentioned objectives were accomplished. The
various compression techniques may be applied for efficient
utilization of bandwidth and storage. This system can be
extended to work on the files containing Unicode characters
as well. This application can be extended to work with other
file formats. By addition of transferring of data from one
system to another, system can be enhanced.
6 CONCLUSION
We can conclude that representation of dynamic hill cipher
and message digest concatenation is more secure than hill
cipher using dynamic key .This algorithm provides high
security in terms of authentication, confidentiality and
integrity of data. The chances of breaking the encrypted data
in cloud computing will decrease too many folds due to the
use of dynamic key length and concatenated message digest.
The reason being, the intruder does not have the dynamic
value of key size. The algorithm is efficient, requires low
maintenance, secure and highly reliable security provider
that protects the valuable data of the users and curbs the
intruder’s attempts to attack that data in cloud computing.
ACKNOWLEDGEMENT
I wish to thank to Mr. Zatin Gupta, Assistant Professor, Raj
Kumar Goel Institute of Engineering & Technology,
Ghaziabad, U.P., India for his valuable guidance and
motivation, throughout the thesis period. Without his
guidance it is not possible for me to complete this work on
time.
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5. IJRREST
INTERNATIONAL JOURNAL OF RESEARCH REVIEW IN ENGINEERING SCIENCE & TECHNOLOGY
(ISSN 2278–6643)
VOLUME-2, ISSUE-2, JUNE-2013
IJRREST, ijrrest.org 72 | P a g e
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