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Journal of Research in Engineering and Applied Sciences
JREAS, Vol. 3, Issue 04, Oct 2018
3-LAYER PC TEXT SECURITY VIA COMBINING
COMPRESSION, AES CRYPTOGRAPHY
2LSB IMAGE STEGANOGRAPHY
1Computer Engineering Department, Umm Al-Qura University, Makkah, Saudi Arabia;
2Computer Sciences Department, Umm Al-Qura University, Makkah, Saudi Arabia
*Corresponding Author Email: aagutub@uqu.edu.sa
Abstract
In today's scenario, one of the biggest challenges facing computer users is how to secure data on a personal computer or in any
communication. Various forms of data security and hiding algorithms have been developed in the last decade. Cryptography
and steganography are known familiar security methods to be used for hide sensitive data. In this paper, we have developed a
data hiding method in images with three security layers. The first layer is compression to reduces the redundancy in data
representation, i.e. to decrease the storage capacity required for that sensitive data. The second layer is cryptography using
the Advance Encryption Standard (AES) to make the compressed data unusable. The third layer hides the data in the 2 least
significant bits (LSB) of images presenting high 3-layers security scheme. The results proven interesting outcomes compared
to other methods. This 3-layer technique is showing promising research direction for further text security developments to be
coming in the future.
Key Words : Security for personal computers, AES cryptography, Image steganography, Hiding text on PC, LSB
steganography, Data compression.
1. Introduction
1 1 1 2 1
Noorah Alanizy , Alanood Alanizy , Noura Baghoza , Manal AlGhamdi , *Adnan Gutub
ISSN (Print) : 2456-6411, ISSN (Online) : 2456-6403
There are several ways to hide sensitive data in a personal
computer (PC). Cryptography and steganography are
known common security methods to hide sensitive data.
Cryptography reorder/replace the data such that it
becomes unbeneficial [1]. Steganography hides the data
within other media so that the hidden information is
invisible to humans [2]. However, there are concerns
about how effective these methods are in terms of
confidentiality, especially if the data is classified sensitive
to the person, such as e-mail messages and credit card
information [3]. This made-up the motivation to benefit
fr o m bo t h, i . e. c o mbin i ng c r ypto g raphy and
steganography assuming more privacy. In fact, this
security combination is assumed to more trusted,
confidential and only to be known by PC user [4].
The research proposes utilizing cryptography process of
converting plain text into unintelligible text, rendering it
unreadable without the secret knowledge [5], merged to
steganography as art or practice of concealing messages,
images, or files within other multimedia message, image,
or file [6].
The objective of this work presents multi-layers of
algorithms to hide sensitive data in an image, similar in
principle to the strategy presented in [7] but hiding within
images instead of videos. This multi-layers proposed
research innovation is designed with its first layer to
reduce the size of the embedded data, i.e. by compressing
the data before encrypting it. Applying the compression
algorithm before encrypting the data helps reduce the size
of data to enable faster and secure transmission, which
furthermore increase the overall speed of the encryption
process. The second layer is cryptography, as the
responsible confidentiality layer applied in the system. In
this step, we are encrypting the secret plain text and
converting it to cipher text using the AES algorithm [8].
Cryptography requires a secret key to be agreed upon
between the sender and receiver for the encryption and
decryption processes [9].
In this work, the sensitive data passes through the crypto
layer after compression to be followed by the
steganography layer, as third layer, resulting in the output
file as trusted Stego-Image [2]. Fig. 1 shows the proposed
3-layers security system. This proposed 3-layer system is
implemented on a software platform using Java
programming language. We assumed cryptography layer
to apply acceptable security using AES algorithm as well
as st ega nog rap hy lay er adopting image-based
steganography, i.e. hiding the encrypted data in the least
significant bits (LSB) of images, similar in theory to
previous work presented in [8].
Fig. 1 : Steps of our proposed system
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2. Background
There are many methods available that can be used to
secure data combining cryptography and steganography
using various multimedia contents motivating this
research. For example, M. Hussain [6] proposed to hide
data bits in an image by changing the LSB of each RGB
image pixel'scolour byte. The method [6] described
storing three bits in each pixel by changing the LSB bit of
the red, green, and blue colour components, since every
colour is represented by a byte. The research showed a
real advantage of using LSB to hide secret data where the
change in the pixels had a very low effect, i.e. unnoticed in
observation, as also been proven in the work presented in
[10]. Each shading RGB cover pixel is of 3 bytes making
24-bits in need for every pixel representation. The 3 bytes
for each pixel is to demonstrate a shading quality hiding
three bits in each chosen pixel. Assume, for example, we
want to hide decimal number 300 in binary form into the
three below adjoining pixels (9 bytes).
10010101 00001101 11001001
10010110 00001111 11001011
10011111 00010000 11001011
This secret number 300 represented as 100101100 in
binary can be embedded into the LSBs as below:
10010101 00001100 11001000
10010111 00001110 11001011
10011111 00010000 11001010
In this way, here the perception expresses that exclusive
5-bits are changed, comparing to the original pixels bits,
out of 9 bits, as typical example of hiding number 300
which is completely affected by the data bits. This LSB
steganography is found revisited in different flavours to
find benefits for different focuses such as the work of
"Pixel Indicator high capacity Technique for RGB image
Based Steganography" [11], or "Vibrant Color Image
Steganography using Channel Differences and Secret
Data Distribution" [12]. The LSB image steganography
even found modifications using truth table methods [13]
which are considered less secure than normal AES crypto
involved systems [14].
Komal Patelet et. al. [15] discussed security method in
which the sensitive message is first encrypted by the
Blow-fish crypto algorithm and then hidden similarly in a
cover file using steganography. The steganography used
was also based on the LSB algorithm for both embedding
and extraction processes. They used C#.Net language to
implement their proposed work in brief description
manner. This multi-level security system is found
common in previous "Triple-A" work discussed in [16].
Satwinder Singhet et. al. [1] and Nouf Al-Otaibi et. al. [8],
both proposed interesting approaches that provide good
security to hide PC data. They encrypt the data via AES
cryptography followed by hiding it within digital images
using LSB image steganography. Nouf system [8] is clear
to analyze since it is designed on visual basic platform.
We tested this Nouf system thoroughly and carried out
this study focusing on improving it reducing the data
hidden capacity proposing this 3-layer PC text security
via combining compression, AES cryptography and
2LSB image steganography.
3. The Proposed System
The 3-layer security system for hiding sensitive text data
has three layers, i.e. a compression data capacity layer
followed by two security layers as illustrated in
framework overview of Fig. 2. The crypto layer is using
the AES algorithm. We implemented AES utilizing
javax.crypto package using a secret key (password) with
of 6-character length. In this layer, each character of the
secret message is converted into an array of binary bytes
providing the result as encrypted ciphertext. Then the
ciphertext of this crypto layer is combined to a header
message containing information about
colour channels used, number of LSBs for stego layer,
and password for encryption. This result of ciphertext and
header passes to the stego layer for LSB imbedding
process.
In the steganography layer the system involves a PC
available RGB image (PNG or BMP) decided by user to
convert its pixels into an array of binary bytes. This stego
layer preparation can start its process while the crypto
layer is running, i.e. preparing the image as binary bits
array, but it cannot start hiding data except after the
cipher-text is generated from the crypto layer. Each pixel
within the RGB image has three channels, namely red,
green and blue (RGB), representing a byte of 8 bits each.
Therefore, using the least significant bits (LSB) image-
based steganography in our original system hides 3 bits in
each pixel as will be detailed and improved in the
interfaces subsections below.
3.1 System Interfaces
The system interface presented is described by the
process showing the platform figures. The program first
runs selection main interface shown in Fig. 3. It asks
about the mechanism to be chosen by the user, i.e.
"Encryption and Hide" or "Decryption and Show".
If the choice is "Encryption and Hide", then the process
will conduct the following procedure:
1. Choose an image to make it a stego cover.
2. Choose the location to save the stego image.
3. Enter secret data as plain text (Fig. 4).
4. Check the “encrypt” checkbox to encrypt the
message.
5. Click next.
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6. The interface has a “view” button to show the
selected image (Fig. 5).
7. Choose the colour channels “R, G or B” to hide the
data on them with “B” as default.
8. Choose the testing number of LSB “1 to 8” to hide
in each channel with “1” as default.
9. Detailed information will appear in the same
window.
10. Click “Merge text with image” as the process is
shown in Fig. 6.
Fig. 2 : Security system crypto - stego layers
Fig. 3 : Main interface
If the choice of main system interface as Fig. 3 is selected
"Decryption and show", then, the process will be as
follows:
1. Choose a stego cover image (Fig. 7).
2. Click “Decryption and show” button.
3. Popup window appear; ask to enter password to
decrypt the secret data (Fig. 8).
4. If password entered correctly, secret message will
appear in the text area.
-- If false password is entered, an error (invalid)
message is shown (Fig. 9).
5. It can save the secret message as a text file (Fig.
10).
6. The interface has a“view” button to show the
selected image (Fig. 11)
Fig. 4 : Stego (encode) interface
Fig. 5 : Image shown when icon “view” is clicked
Fig. 6 : System interface showing detailed
information of the encoding process
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4. Testing and Verification
The research studied images comparing them before and
after steganography. It involved several images for the
testing and verification process providing very similar
results. The comparison of all original images vs. stego-
images is remarking that hiding data in a stego image can
work fine only using 1LSB and 2LSB as the stego image
appears the same as the original image, i.e. providing
acceptable security. This issue of using more LSBs is
elaborated in the following subsection relating it to
capacity improvement.
Fig. 7 : Decryption showing interface: “Decoding”
Fig. 8 : Password 'key' popup window
Fig. 9 : Wrong 'invalid' password entered
4.1 Capacity vs. Security
To improve capacity of the proposed security system
multi-bits steganography is used. However, increasing
the LSBs is degrading the system security. Fig. 12
presents
seven images with data hiding in 1,2,3… 7 LSBs. We
observe that when hiding data in 1 and 2 LSBs, the
changes are not noticeable providing acceptable security.
But when hiding data in 3,4,5,6, and 7 LSBs, the image
distortion appears rendering the main objective of the
system.
Fig. 10 : Decryption interface
Fig. 11 : Image shown when “view” button is clicked
The study also examined hiding small amount of data in a
critical comparison resulting negligible image distortion.
This lead to the recommendation of trying storing data in
large-sized images that contains more pixels to avoid
noticeable distortion. Fig. 13 shows a sample of three
testing images, which are stego covers that hide data in
1LSB and 2LSB proving the concept of acceptable
security adopting 2LSB steganography. This suggestion
of using 1LSB as well as 2LSB is analyzed independently
in the following subsection.
The research work further tested several different PC
images with the same extensions of PNG assuming
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different numbers of pixels to be used as cover images, i.e.
for the stego layer shown in Fig. 14. We found that when
hiding the sensitive text in 1LSB and 2LSB, the stego
image does not have any noticeable distortion on it as
pretended also within others work [17]. Moreover, the
two Least Signification Bit (2LSB) steganography
increased the capacity of hiding information double the
usage of 1LSB with acceptable security, as mentioned in
paper [18].
Fig. 12 : Original image followed by
images with data hiding in 1, 2, 3, 4, 5, 6, 7 LSBs
Fig. 13 : Original image followed by
stego-images hiding data in 1LSB and 2LSB
4.1 Considerations and Remarks
Considering the future work suggested by paper [8],
which suffers language flexibility, it suggests making the
system to support different languages, i.e. specified for
Arabic language. It was found that the original work was
implemented using the Visual Basic programming [8],
which do not support Arabic string Unicode texts directly.
A number of adjustments steps are required to solve this
problem. In our improved implementation, we modeled
this 3-layer security system using Java platform, which
supports Arabic string Unicode, CharsetDecoder and
CharsetEncoder, directly. Notes that Java programming
uses Unicode as native encoding, so any text will be
converted to Unicode for proper handling. Java already
supports almost all known encodings [19], making it the
practical choice to be selected for language consideration.
The paper [8] also suggested testing its 2-layer system by
using other cryptographic symmetric algorithm for
possible improvements. Through research [20], AES is
currently found to be the most efficient crypto algorithm
in security features, as shown in Table 1.
Fig. 14 : Different PC images used for testing
as cover images for the stego layer.
Table 1
Comparison of Symmetric Cryptography Algorithms [20]
Algorithms
Blow
Fish
AES
3DES
DES
Key
size
(bits)
32-
448
128,
192,
256
112 or 118
64
Block size
(bits)
64
128
64
64
Round
16
10, 12, 14
84
16
Structure
Feistel
Substitution
Permutation
Feistel
Feistel
Flexible
Yes
Yes
Yes
No
Features
Secure
enough
Excellent
Security
Adequate
security
Replacement
for DES,
Not
structure,
Enough
Speed
fast
fast
Very slow
slow
The paper [8] suggested studying the capacity and
security for practical applications. Therefore, we
involved addition of a pre-security layer to the system,
namely a compression layer, before the cryptographic –
steganography layers. Data compression in cryptography
is believed important in reducing the number of bits for
text that would be hidden in images. Compression data
can save storage capacity contribution in speed up of the
encryption process.
Text compression can be described as removing all
unneeded characters, inserting a single repeat character to
indicate a string of repeated characters and substituting a
smaller bit string for a frequently occurring bit string.
Compression is often compared to data deduplication, but
the two techniques operate differently. Deduplication is a
type of compression that looks for redundant chunks of
data across a storage or file system and then replaces each
duplicate chunk with a pointer to the original. We use the
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5. Conclusions
This study presented 3-layer PC text security via
combining compression, AES cryptography and 2LSB
image steganography in a Java platform system. The
testing involved compression to be performed on the
sensitive data to be secured to increase the capacity. After
compression, the data is processed to cryptography
followed by steganography. The system is implemented
intentionally on a Java platform to benefit from multi-
language flexibility using Eclipse IDE. The study
considered AES cryptography since its found the practical
symmetric crypto procedure. For image steganography,
we have used the simplest yet most effective method
GZIP compression technique which is based on the
Deflate algorithm. Deflate is a lossless data compression
algorithmand associated file format that uses a
combination of the LZ77 algorithm and Huffman coding
supported fully by our Java Platform [19].
4.1 Comparisons and Analysis
In our proposed approach, we use the compression
followed by security encryption and stego techniques.
The compression and security are performed in sequence
processes. In fact, we notice that these procedures
consume less execution time compared to independent
encryption/decryption and stego techniques as shown in
the tables below. In general, joint compression and
security algorithms are more efficient than independent
algorithms. Since the encryption is done after
compression, these algorithms provide higher processing
speeds.
Security: In the combined compression, encryption and
stego techniques, the compression process includes one
or more encryption steps. In addition, a separate
encryption process is tested after compression. As a
result, the combined compression and encryption
technique provides same levels of security when
compared to the independent compression, encryption,
stego techniques.
Performance: Using compression combined to security
encryption and stego algorithms is more effective than
separating all algorithms. This is because when the
encryption is performed after compression, some
unnecessary interfacing routines are found slowing the
overall process. This made-up the confidence of
providing high security speed via combining the 3-layers
of compression, cryptography and steganography, as
detailed in Table 2 for the different timings of hiding
process and Table 3 for the different timings of retrieving
process. In other words, our study has shown that the joint
procedures of compression followed by encryption and
steganography algorithms can increase the system overall
speed more than independently running the algorithms.
This fact of this performance issue is getting more clear as
the size of data increase in real life applications.
known as 2LSB image steganography algorithm which is
found appropriate compared to different higher LSB
stego attempts.
Table 2
Execution Time in Hiding Process
Screenshot for Analysis and
Verification
Security
Co mpress io n
Execution
tim e
(seconds)
Yes
Yes
0.5596
Yes
No
0.5749
No
Yes
0.2217
No
No
0.2307
Table 3
Execution Time in Retrieving Process
Screenshot for Analysis and
Verification
Se cu ri ty
Co m pression
Ex ec utio n
(secon ds )
Yes
Yes
4,9085
Yes
No
5.5197
No
Yes
0.0204
No
No
0.0264
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Acknowledgment
Authors would like to thank Umm Al-Qura University
(UQU) for hosting this research. Special thanks to the
cooperation between the two departments via Prof. Adnan
Gutub from Computer Engineering and Dr Manal
AlGhamdi from Computer Sciences for motivating this
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