Secure Information Exchange System for
Criminal Cases
Aye Mya Thwe
Abstract - For electronic data transmission system, the
adequate security demand grows high over the decades.
There are many distinctive security algorithms to support
the security requirements. The aim of this work is to provide
secure information exchange system for criminal cases. The
culprit record in criminal cases may be text, image and
audio files. To provide confidentiality of these files, different
kinds of symmetric algorithms such as Blowfish, Twofish
and AES are used. The encrypted files (text, image and
audio) of culprit record are organized by using Ionic
compression method to transfer over the communication
medium. This system is implemented by C# programming
language.
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 plays 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 available and
used in information security. They can be categorized
into Symmetric (private) and Asymmetric (public) keys
encryption [3]. Symmetric key algorithms are the fastest
and most commonly used type of encryption [4].
Encryption is applied by combining other techniques in
order to attain a high degree of data security system. This
paper aims to develop an efficient and secure information
exchange system between communities. In this work,
three different kinds of symmetric encryption algorithms
are used to achieve 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. 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.
First Author Name, Department of Information Technology, Aye
Mya
Thwe,
Mandalay
Technological
University,
(email:
ayelaymtu@gmail.com),
Mandalay,
Republic
of
Myanmar,
+959423660204.
Then, encryption and decryption of images using
secret-key block cipher called 64-bits Blowfish was also
described in [6]. The main aim of this work is to get the
best security/performance tradeoff over existing ciphers.
After that, Bismita and his fellow presented about
encryption on MP3 compression. In their approach, they
proposed the encryption technique at the time of
compression to provide security to the online music
transmission and distribution in [5]. For providing more
security to MP3 data transfer, they applied the AES
encryption algorithm to the whole quantized audio data.
According to the literature from these papers, this
paper is proposed a multimedia data security system
using symmetric cryptographic algorithms and
compression technique for criminal cases.
III. OVERVIEW OF CRYPTOGRAPHY AND
ENCRYPTION
Cryptography is the science of information security.
The word is derived from the Greek kryptos, meaning
hidden. Cryptography is closely related to the disciplines
of cryptology and cryptanalysis. Cryptography includes
techniques such as microdots, merging words with
images, and other ways to hide information in storage or
transit. However, in today’s computer-centric world,
cryptography is most often associated with scrambling
plaintext (ordinary text) into ciphertext (a process called
encryption), then back again (known as decryption).
Individuals who practice this field are known as
cryptographers.
Modern cryptography concerns itself with the
following four objectives:
1. Confidentiality_ the information cannot be
understood by anyone for whom it was
unintended
2. Integrity_ the information cannot be altered in
storage or transit between sender and intended
receiver without the alteration being detected
3. Non-repudiation_ the sender of the information
cannot deny at a later stage his or her intentions
in the creation or transmission of the information
4. Authentication_ the sender and receiver can
confirm each other’s identity and the
origin/destination of the information [7]
In cryptography, encryption is the process of encoding
messages (or information) in such a way that third parties
cannot read it, but only authorized parties can. Encryption
doesn’t prevent hacking but it prevents the hacker from
reading the data that is encrypted. In an encryption
scheme, the message or information (referred to as
plaintext) is encrypted using and encryption algorithm,
turning it into an unreadable ciphertext. This is usually
done with the use of an encryption key, which specifies
how the message is to be encoded. Any adversary that
can see the ciphertext should not be able to determine
anything about the original message. An authorized party,
however, is able to decode the ciphertext using a
decryption algorithm that usually requires a secret
decryption key, that adversaries do not have access to [8].
There are two general categories for key-based
encryption – symmetric (secret key) and asymmetric
(public-key).
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. In public-key encryption schemes, the
encryption key is published for anyone to use and encrypt
messages. However, only the receiver party has access to
the decryption key and is capable of reading the
encrypted messages [8].
message is first divided into 32 bits. The left 32 bits are
XORed with the first element of a P-array to create a
value called P´, run through a transformation function
called F, then XORed with the right 32 bits of the
message to produce a new value called F´. Then F´
replaces the left half of the message and P´ replaces the
right half, and the process is repeated 15 more times with
successive members of the P-array. The resulting P´ and
F´ are then XORed with the last two entries in the P-array
(entries 17 and 18), and recombined to produce the 64-bit
ciphertext.
Because Blowfish is a symmetric algorithm, the same
procedure is used for decryption as well as encryption.
The only difference is that input to the encryption is
plaintext; for decryption, the input is ciphertext [12].
IV. SYMMETRIC ENCRYPTION ALGORITHMS
Symmetric encryption is the oldest and best-known
technique. It uses a single secret key to encrypt and
decrypt the message. A secret key, which can be a
number, a word, or just a string of random letters, is
applied to the text of message to change the content in a
particular way [9]. As a basis, there are two types of
symmetric encryption: stream cipher and block cipher.
Stream ciphers encrypt the bits of information one at
time - operate on 1 bit (or sometimes 1 byte) of data at a
time (encrypt data bit-by-bit) [10].
Block cipher is a symmetric cipher which encrypts a
message by breaking it down into blocks and encrypting
data in each block [11].
There are various kinds of block cipher algorithms:
AES, Blowfish, CAST5, DES, IDEA, RC6, Serpent,
Triple DES and Twofish. At the proposed system,
symmetric block cipher algorithms are used. Blowfish is
used for text encryption, Twofish is applied for image
encryption and AES is for audio.
B. AES Encryption Algorithm
AES is a non-Feistel cipher that encrypts and decrypts
a data block of 128 bits. It uses 10, 12, or 14 rounds. The
key size, which can be 128, 192 or 256 bits, depends on
the number of rounds [13]. The input data is 16 bytes, and
the resulting encrypted data is also 16 bytes. The larger
the key size is used, the more difficult it is to break the
algorithm and obtain the encrypted data.
A. Blowfish Encryption Algorithm
Blowfish is a symmetric encryption algorithm,
meaning that it uses the same secret key to both encrypt
and decrypt the message.
= XOR
Plaintext
Plaintext
Round 1
Expand Key
Add Round Key
Substitute Bytes
Inverse Sub Bytes
Shift Rows
Inverse Shift Rows
Mix Columns
Add Round Key
Round 10
W[0,3]
Inverse Mix Columns
W[4,7]
Add Round Key
Inverse Sub Bytes
Round 9
Add Round Key
Inverse Shift Rows
Shift Rows
Mix Columns
Add Round Key
Inverse Mix Columns
W[36,39]
Round 10
Inverse Shift Rows
Shift Rows
Add Round Key
Add Round Key
Inverse Sub Bytes
Substitute Bytes
Round 1
Round 9
Substitute Bytes
W[40,43]
Add Round Key
Ciphertext
Ciphertext
Figure 2. Structure of AES algorithm
Plaintext
64
32
32
P1
P1'
F
P1'
F1'
P2
P2'
P2'
F
F2'
( 13 more iterations)
P15'
F15'
P16
P16'
F
P16'
F16'
P17
P18
32
32
64
Ciphertext
Figure 1. Blowfish algorithm
Blowfish is also a block cipher, meaning that it divides
a message up into fixed length blocks during encryption
and decryption. The block length for Blowfish is 64 bits;
messages that aren’t a multiple of eight bytes in size must
be padded.
A graphical representation of the blowfish algorithm
appears in figure 1. In this description, a 64-bit plaintext
The structure of the AES is shown in figure 2. AES
operates on a 4×4 column-major order matrix of bytes,
termed the state. It consists of add round key at initial
round. Add round key operates each byte of the state is
combined with the round key using bitwise xor. The first
r-1 rounds (r is 10, 12 or 14) are similar and they consists
of 4 transformations:
1. SubBytes- a substitution step where each byte is
replaced with another according to a lookup
table.
2. ShiftRows- a transposition step where each row
of the state is shifted cyclically a certain number
of steps.
3. MixColumns- a mixing operation which
operates on the column of the state, combining
the four bytes in each column.
4. AddRoundKey- each byte of the state is
combined with the round key using bitwise xor.
The last round has only 3 transformations
1. SubBytes
2. ShiftRows
3. AddRoundKey [14].
C. Twofish Encryption Algorithm
Twofish is a 128-bit block cipher that accepts a
variable-length key up to 256 bits. The cipher is a 16round Feistel network with a bijective F function made up
of four key-dependent 8-by-8-bit S-boxes, a fixed 4-by-4
maximum distance separable matrix over GF(2 8), a
Pseudo-Hadamard Transform, bitwise rotations, and a
carefully designed key schedule.
Figure 3 shows an overview of the Twofish block
cipher. Twofish uses a 16-round Feistel-like structure
with additional whitening of the input and output. The
only non-Feistel elements are the 1-bit rotates. The
plaintext is split into four 32-bit words. In the input
whitening step, these are XORed with four key words.
This is followed by sixteen rounds. In each round, the two
words on the left are used as input to the g functions.
(One of them is rotated by 8 bit first). The g function
consists of four byte-wide key-dependent S-boxes,
followed by a linear mixing step based on an MDS
matrix.
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
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 3. Structure of Twofish algorithm
Original data
Original
data
Text
(.txt)
Image
(.jpg)
Secret
key
Encryption
Secret
key
Twofish
algorithm
Audio
(.wav)
Database
Image
(.jpg)
Text
(.txt)
Audio
(.wav)
Twofish
algorithm
Blowfish
algorithm
AES
algorithm
Database
Secret
key
Blowfish
algorithm
AES
algorithm
Secret
key
Secret
key
Decryption
Secret
key
Ciphertext
Encrypted data
Encrypted data
Compression
Ionic zip compression
Ionic zip compression
Decompression
Final data
Compressed data
Compressed data
Received data
Process of Sender
Process of Receiver
Ciphertext
Send
Figure 4. Proposed System Design
As illustrated in figure, the proposed system has two
portions: sender site and receiver site. From the sender
site, the culprit’s record (text, image and audio) are
loaded from the database. The text file (.txt) is encrypted
with a secret key using Blowfish encryption algorithm.
Then the image (.jpg) of culprit is encrypted with
Twofish algorithm and AES is used to encrypt the audio
file (.wav). All the ciphertexts (encrypted text, encrypted
image and encrypted audio) are compressed using ionic
zip compression method to obtain all in one. Then, the
compressed file is transmitted to the receiver through the
mail server.
At the receiver site, the received file is firstly
decompressed and then decrypted with the secret keys
using corresponding algorithms to get back the original
data.
VI. IMPLEMENTATION OF THE PROPOSED SYSTEM
The implementation of the proposed system is
presented with a series of interfaces. When the user starts
the system, the welcome window form will be appeared
as the shown in figure 5.
The results of the two g functions are combined using
a Pseudo-Hadamard Transform (PHT), and two keywords
are added. These two results are then XORed into the
words on the right (one of them is rotated left by 1 bit
first, the other is rotated right afterwards). The left and
right halves are them swapped for the next round. After
all the rounds, the swap of the last round is reversed, and
the four words are XORed with four more keywords to
produce the ciphertext [15].
V. PROPOSED SYSTEM DESIGN
To develop the proposed system, three symmetric
encryption algorithms which give good protection to the
culprit’s record (including text, image and audio) are used
and ionic compression technique is also used to compact
the encrypted culprit records’ files. In the proposed
system, 128-bit key length is chosen to use for three
algorithms. The proposed system design is illustrated in
figure 4.
Figure 5. Welcome Form
Firstly, the user has to click the go button to continue
the system. Then the log in form will be appeared as
shown in figure 6.
If the user wants to view the culprit’s image and
information in detail, he or she can easily search by
filling the culprit’s name and his other information in the
search form as illustrated in figure 10.
Figure 6. Login Form
In this form, the user has to fill the information such as
user name and password to log in the system. So, this
user must be registered person and he or she must be
authorized person to manage the system. Then, the user
can see the main window form.
Figure 10. Search Form
The user can transfer the culprit’s record from one
police station to another via email. To send the
information secretly, firstly the culprit’s record is chosen
from the database as shown in figure 11.
Figure 7. Main Form
This user can edit, update, delete or transfer the culprit
information from the database. The culprit information
form is shown in figure 8.
Figure 11. Send Form
Figure 8. Culprit Information
Before sending, the chosen culprit’s record must be
encrypted with corresponding encryption algorithms.
Figure 12: shows the encryption of text file with Blowfish
algorithm.
The user can update the culprit’s record as illustrated
in figure 9.
Figure 12. Text Encryption with Blowfish Algorithm
Figure 9. Update Form
Figure 13 illustrates the image encryption with
Twofish encryption algorithm.
At the receiver site, the original information of culprit
can be got back by processing the reverse order as the
sender site.
Our system is intended to save time, money and human
resources when transmitting the culprit’s information
from one police station to others. Moreover, because of
being a computer-based system, it also protects the
problems caused by paper-based system. Furthermore, it
also promises the information jumping while transmitting.
Figure 13. Image Encryption with Twofish Algorithm
The audio encryption using AES encryption is shown
in figure 14.
Figure 14. Audio Encryption with AES Algorithm
After that, these encrypted files are pressed tightly
together using ionic compression method.
VII. CONCLUSIONS
In today, various data exchange systems have been
developed to exchange text, image, audio and other
multimedia data between communities. Therefore,
security of multimedia data transmitted over the
unsecured medium is an imperative issue. Usually, fast
and powerful encryption algorithms are very attractive for
multimedia
applications.
Symmetric
encryption
algorithms are faster to encrypt multimedia data and
easier to implement than asymmetric encryption
algorithms. This system is intended to apply in the urgent
data transmission about culprit between police stations. In
this work, only symmetric encryption algorithms are used
to encrypt the data. As further extension, a more robust
security system can be developed by combining
symmetric and asymmetric encryption algorithms.
ACKNOWLEDGMENT
I wish to express my profound gratitude to Ministry of
Science and Technology for encouraging to perform
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
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]
Figure 15. File Compression with Ionic Compression
[2]
Then, the compressed file is send to the intended
receiver through the mail server.
[3]
[4]
[5]
[6]
Figure 16. File Transmission to the Intended Receiver
[7]
[8]
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