Secure Information Exchange System for
Criminal Cases
Aye Mya Thwe
Abstract –Nowadays, networks like internet applications supply
essential communication between millions of people as well as the
security of information transmitted over the unsecured networks
becomes a tremendously important fact. Therefore, different kinds
of security features are used to meet the security demand. This
paper presents a proposed model to provide the information secrecy
for criminal cases. With the help of proposed technique of
encryption and decryption, ciphertext or encrypted text will be
generated and plaintext (.txt and .jpg) or decrypted text will be
gotten by applying the reverse process. To support confidentiality of
plaintext, two different kinds of symmetric algorithms such as
Blowfish and Twofish are used. To transfer over the communication
channel, the encrypted files are compacted with Ionic compression
method. C# programming language is used to implement the
system.
Keywords
-
compression, cryptography, encryption,
security, symmetric encryption algorithms
I. INTRODUCTION
The computer and communication technology’s today
are very important parts for a strong economy, thus it is
important to have suitable security standards systems and
technologies to meet that security needs [1]. To provide
the security requirement, cryptography stands a major
role.
Cryptography underlines many of the security
mechanisms and builds the science of data encryption and
decryption. Cryptography enables us to securely store
sensitive data or transmit across insecure networks such
that it cannot be read by anyone except the intended
recipient. By using a powerful tool such as encryption we
gain privacy, authenticity, integrity, and limited access to
data [1].
Many encryption algorithms are widely attainable and
utilized for information security. There are two basic
types of encryption algorithm: Secret Key Cryptography
which is also known as Symmetric Key Cryptography
and Public Key Cryptography which is also known as
Asymmetric Key Cryptography. Symmetric Key
Algorithms are the quickest and most commonly used
type of encryption. Encryption can be used to protect
information, but some other techniques are still needed to
make security, particularly to verify the message
authenticity and integrity. This paper aims to build an
efficient and strengthen information exchange system
between communities. In this work, two distinctive types
of symmetric encryption algorithms are used to succeed
good security and a compression technique is applied to
be more convenient in data transfer.
II. RELATED WORKS
In the present, several security features have applied to
make the data secure from various attacks and for the
integrity of data.
First Author Name, Department of Information Technology, Aye
Mya
Thwe,
Mandalay
Technological
University,
(email:
ayelaymtu@gmail.com),
Mandalay,
Republic
of
Myanmar,
+959423660204.
In [2], the authors carried out a research to optimize
the existing standards of cryptography (AES) for the
images and text data encryption. The basic aim of their
work is to modify AES to provide less computation and
better security for data.
Then, encryption and decryption of images using
secret-key block cipher called 64-bits Blowfish was also
described in [3]. The main aim of this work is to get the
best security/performance tradeoff over existing ciphers.
This paper is intended to develop a security system for
multimedia data about criminal cases by applying
symmetric key algorithms and compression method.
III. OVERVIEW OF CRYPTOGRAPHY
“Cryptography” derives from the Greek word kruptos,
meaning “hidden”. Cryptography enables to store
sensitive information or transmit it across insecure
networks (like the Internet) so that it cannot be read by
anyone except the intended recipient.
A cryptographic algorithm, or cipher, is a
mathematical function used in the encryption and
decryption process. A cryptographic algorithm works in
combination with a key-a word, number, or phrase-to
encrypt the plaintext. The security of encrypted data is
entirely dependent on two things: the strength of the
cryptographic algorithm and the secrecy of the key. A
cryptographic algorithm, plus all possible keys and all the
protocols that make it work comprise a cryptosystem.
There are two basic types of cryptography: Symmetric
Key (Secret Key Cryptography) and Asymmetric Key
(Public Key Cryptography).
In secret key cryptography, a single key is used for
both encryption and decryption. As shown in figure 1, the
sender uses the key (or some set of rules) to encrypt the
plaintext and sends the ciphertext to the receiver [4].
Hello
Plaintext
Encryption
Hello
Plaintext
A1@
cipher
Decryption
Figure 1. Secret Key Cryptography
In public key cryptography, two keys are used: one for
encryption (public key) and other is decryption (private
key). Although public key is published for anyone to use
and encrypt messages, only the recipient has access to the
private key that capable of reading the encrypted
messages.
Plaintext (64 bits)
Hello
Plaintext
32
Hello
Plaintext
P1
P2
Encryption
(Receiver Public Key)
A1@
cipher
32
+
F
+
F
+
+
Encryption
(Receiver Private Key)
13
iteration
Figure 2. Public Key Cryptography
IV. SYMMETRIC ENCRYPTION ALGORITHMS
Symmetric keys encryption or secret key encryption
use only one key is used to encrypt and decrypt data. The
key should be distributed before transmission between
entities. Keys play an important role in encryption and
decryption. If weak key is used in algorithm then
everyone may decrypt the data. Strength of the symmetric
key encryption depends on the size of the key used. For
the same algorithm, encryption using longer key is harder
to break than the one done using smaller key [5].
Symmetric key cryptographies are generally categorized
as stream ciphers and block ciphers.
Stream ciphers operate on a single bit (byte or
computer word) at a time [4].
A block cipher is so-called because the scheme
encrypts one block of data at a time using the same key
on each block [4].
There are a number of block cipher algorithms such as
RC2, AES, DES, Triple DES, Twofish, RC6 and
Blowfish. Symmetric key block ciphers are used at the
proposed system. For text encryption, Blowfish is applied
and Twofish is used for image encryption.
P16
+
+
F
P18
P17
+
+
32
32
Ciphertext (64 bits)
Figure 3. Feistel Structure of Blowfish Cipher
B. Twofish Encryption Algorithm
In cryptography, Twofish is a symmetric key block
cipher with a block size of 128 bits and key sizes up to
256 bits. Twofish’s distinctive features are the use of precomputed key-dependent S-boxes, and a relatively
complex key schedule. Twofish borrows some elements
from other designs; for example, the Pseudo-Hadamard
Transform (PHT) from the SAFER family of ciphers.
Twofish has a Feistel structure like DES [7].
Plaintext(128 bits)
K0
K1
F
K2
g
K2r+8
S-box 0
S-box 1
S-box 2
K3
Input
whitening
<<<1
PHT
MD
S
S-box 3
A. Blowfish Encryption Algorithm
Blowfish, a symmetric block cipher, uses a Feistel
network, 16 rounds of iterative encryption and decryption
functional design. The block size of blowfish algorithm is
64 bits, and the key size may be of any length but having
a limit up to 448 bits. The power of the blowfish
algorithm relies on its sub-key generation and its
encryption.
Blowfish cipher uses 18 each of 32-bit sun arrays
commonly known as P-boxes and four Substitution boxes
each of 32 bit size and having 256 entries each. It uses a
Feistel cipher which is a general method of transforming
a function into another function by using the concept of
permutation. The working of blowfish cipher can be
illustrated as follows,
It splits the 64 bit block into two equal blocks having
32 bit size each. Left block is XORed with first sub array
P1 and then obtained result is fed into a function called Ffunction. Inside the F-function substitution operations are
carried out which in turn converts 32 bit blocks into
another 32 bit blocks. Then resulted 32 bit entries are
XORed with the right half and the result obtained is
swapped with the left half for the next round. So, after the
successful completion of each round right half becomes
the new left half or vice versa and Feistel structure is
followed up to 16 rounds. The resultant left and right
halves are not swapped but XORed with the seventeenth
and eighteenth P-arrays. The Feistel structure of blowfish
algorithm is shown in the figure 3[6].
One round
g
S-box 0
S-box 1
<<<8
S-box 2
MD
S
S-box 3
K2r+9
>>>1
15 more
rounds
Undo last
swap
K4
K5
K6
K7
Output
whitening
Ciphertext(128 bits)
Figure 4. Structure of Twofish algorithm
Figure 4 shows an overview of the Twofish encryption
algorithm. The two words on the left are used as input to
the g functions after the rotations by 8 bits of one of
them. The g function consists of four byte-wide keydependent S-boxes, followed by a linear mixing step
based on an MDS matrix. The results of the two g
functions are combined using a Pseudo-Hadamard
Transform (PHT), and two keywords are added. One of
the words on the right is rotated by 1 bit and then both of
them are XORed into the results on the left. The left and
right halves are then swapped for the next round. After 16
rounds, the swap of the last round is reversed, and the
four words are XORed with four more key words to
produce the ciphertext [8].
V. PROPOSED SYSTEM DESIGN
The proposed system utilizes two symmetric
algorithms for encryption which supply high security to
the culprit’s record. And, to be more convenient the data
transfer, ionic compression is used too. The same key
length (128 bits) is used for two algorithms. There are
two portions in the proposed system design. The
following figure 5 and figure 6 illustrate the process of
sender site and receiver site.
Secret key
Encrypt with Blowfish
Algorithm
Plaintext
Q!r@#12ter#8@%
^{+)io*;’ab5(!~9?/”\e0>,:ng$
Ciphertext
Ionic Zip Compression
Database
Aung thiha
Aung Lay
U Hla Khin
Compressed
File
Send
Encrypt with Twofish
Algorithm
Figure 7. Welcome Form
Secret key
After clicking the start button, the log in form will
appear as shown in figure 8.
Figure 5. Process of Sender Site
As illustrated in figure 5, initially, the user has to load
the culprit record (text and image) from the database. The
text file (.txt) is encrypted with a secret key using
Blowfish algorithm. Then, the image file (.jpg) is
encrypted with another key but same length using
Twofish algorithm. And then, the ciphertexts, encrypted
text and image, are compressed with ionic zip
compression technique. After that, the compressed file is
transmitted to the intended receiver through the mail
server.
At this form, user name and password has to fill by the
user to log in the system. If this user is authorized person,
the main window form (figure 9) can be seen.
Secret key
Compressed
File
Decrypt with Blowfish
Algorithm
Ciphertext
Aung thiha
Aung Lay
U Hla Khin
Plaintext
Database
Received
data
Ionic Zip Compression
Q!r@#12ter#8@%
^{+)io*;’ab5(!~9?/”\e0>,:ng$
Figure 8. Login Form
Decrypt with Twofish
Algorithm
Secret key
Figure 6. Process of Receiver Site
The decryption process of receiver site is shown in
figure 6. The procedure of receiver site is the reverse of
the sender’s. The original data is recovered by
decompressing and decrypting with the keys those are
employed in the encryption.
VI. IMPLEMENTATION AND RESULT
The following results are generated by implementing
the proposed system. In this paper, the results are
displayed with a series of interfaces. Firstly, the user can
see the welcome window form as main interface and can
continue by pressing start button as shown in figure 7.
Figure 9. Main Form
In this form, the user can do the work such as editing,
updating, deleting or transferring about the culprit’s
information from the database. Figure 10 shows the
information of culprit.
Figure 10. Culprit Information
As illustrated in figure 11, the user can update the
culprit record.
Figure 13. Send Form
For the security purpose, the culprit’s record that
would like to transfer must be encrypted with
corresponding encryption algorithms before sending.
Figure 14 shows the text encryption result using
Blowfish.
Figure 11. Update Form
The user can easily search the culprit’s image and
information by filling the culprit’s name and his other
information by using search form (figure 12).
Figure 14. Text Encryption with Blowfish Algorithm
The encryption result of image file applying Twofish
algorithm is illustrated in figure 15.
Figure 12. Search Form
Figure 15. Image Encryption with Twofish Algorithm
The culprit’s record from the database can be
transferred from one police station to another via email
by utilizing send form (figure 13).
And then, these encrypted files are compressed with
ionic compression technique to obtain all in one.
the facilities throughout the research. Moreover, the
author would also like to express her appreciation and
thanks to her all the respected teachers from Department
of Information Technology, Mandalay Technological
University, beloved parents and her close friends for their
invaluable suggestions and their kind help through this
work.
[1]
[2]
Figure 16. File Compression with Ionic Compression
[3]
After all, the compressed file is send to the recipient
via the mail sever.
[4]
[5]
[6]
[7]
[8]
Figure 17. File Transmission to the Intended Receiver
At the recipient, the original information of culprit can
be obtained by processing the reverse operation as the
sender site.
The proposed system is designed to provide good
protection for transferring culprit’s information between
police stations. Because of computer-based system, it also
promises saving time, money and human resources.
VII. CONCLUSIONS
Today’s crypto world, various encryption techniques
are used to prevent the multimedia content from
unauthorized users. This paper proposes a security system
which provides good security to the culprit’s record (.txt
and .jpg). In this work, two symmetric encryption
algorithms are used to encrypt the text data and image. As
further extensions, hybrid cryptosystems can be designed
using the combination of both symmetric and asymmetric
(public-key) encryption algorithms. Furthermore,
culprit’s record about criminal cases such as audio and
video files can be attempted for encryption processes.
ACKNOWLEDGMENT
I wish to express my profound gratitude to Ministry of
Science and Technology for encouraging to performed
researches. The author would also like to express her
appreciation and thanks to Dr. Su Wai Phyo, Associate
Professor, Department of Information Technology,
Mandalay Technological University for her supporting
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