International Journal of Engineering Trends and Technology- Volume2Issue3- 2011
A Novel Approach of Multilevel Binary Image
Encoding using Walsh Table and Spiral Scanning
Nilanjan Dey#1, Sourav Samanta#2, Anamitra Bardhan Roy#3
#1
IT Department, JIS College of Engineering, Kalyani, Nadia-741235, West Bengal, INDIA
CSE Department, JIS College of Engineering, Kalyani, Nadia-741235, West Bengal, INDIA
#3
CSE Department, JIS College of Engineering, Kalyani, Nadia-741235, West Bengal, INDIA
#2
Abstract— In this paper we proposed a method of image
encoding technique in a new formulated way. During
transmission image is encoded in two phases for the
enhancement of security. In the first phase encoding is done
using Walsh table and in the second phase by using spiral
scanning based encoding technique.
Keywords— Image Encoding, Dual-Encoding, Walsh table, Spiral
Encoding.
I.
INTRODUCTION
Image encoding enhanced the security remarkably.
Embedding encoded messages or images in stenographic
system can be carried out with many different technique
namely LSB, DCT, DWT, etc.
Steganography [1, 2, 3] is the process of hiding of a secret
message within an ordinary message and extracting it at its
destination. Anyone else viewing the message will fail to
know it contains secret/encrypted data. The word comes from
the Greek word “steganos” meaning “covered” and “graphei”
meaning “writing”.
Encoding of the secrete image can be perform in many
different ways like LAR Codec [4], XOR transformation [6],
G-Scan [5], etc.
To modify the technique of image encoding for betterment
we tried to propose a new methodology to encode an image
using Walsh table and spiral based scanning. This Dual-layer
Encoding technique is carried out for the purpose of two fold
security.
II.
As an example,
W1 = [+1]
W4 =
+1 +1
W2 = +1 -1
+1
-1
+1
-1
+1
+1
+1
+1
+1
-1
+1
-1
These sequences are Walsh codes and can be derived from
a binary Walsh matrix.
A station sends out its chip sequence to send a 1 and its
inverse to send a 0 (or +1 and a -1; zero being silence).
For our further computational we will use binary Walsh
Matrix.
III. SPIRAL SCANNING AND ENCODING
TECHNIQUE
Scan the elements of 2-D array using spiral fashion and
store the elements into a 1-D array.
1 2 3
4
6 7 8
9
11 12 13 14
16 17 18 19
21 22 23 24
WALSH TABLE
In Carrier Sense Multiple Access (CDMA) procedure one
of the efficient ways to generate orthogonal code sequences is
Walsh table [7]. Each row of a Walsh table is an orthogonal
code sequence.
The tables can be generated recursively, provided that K is
power of two.
W1 = [+1]
W2N = WN
WN
+1
+1
+1
+1
5
10
15
20
25
Figure 1
Scan the generated 1-D array and store elements in a 2-D
array to generate encoded array.
1
2
3
4
5
10
15
20
25
24
Figure 2
WN
WN
ISSN: 2231-5381 http://www.internationaljournalssrg.org
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International Journal of Engineering Trends and Technology- Volume2Issue3- 2011
1
10
23
6
19
2
15
22
7
18
3
20
21
8
17
4
25
16
9
12
5
24
11
14
13
First Phase Decoding:
7. Perform XOR operation between the elements of the
first phase decoded matrix and the Walsh matrix at
respective positions to get back the original secret
image.
Figure 3
Decoded array is generated by linearly scanning elements
from the above array and store the elements in spiral way into
a separate 2-D array.
1
2 3 4
6 7 8 9
11 12 13 14
16 17 18 19
21 22 23 24
5
10
15
20
25
V. RESULT AND DISCUSSION
The First and Second phase encoded and decoded image is
shown below,
Encoding by Appling Walsh Table:
Figure 4
IV. PROPOSED METHOD
First Phase Encoding:
1.
2.
3.
The size of the secret binary image is computed.
A Walsh table is generated considering -1 as 0 of
the same size as the binary image.
XOR operation is performed between the
elements of the image matrix and the Walsh
matrix at respective positions.
(a)
(b)
Encoding by Appling Spiral Scanning:
Second Phase Encoding:
1. The generated encoded image from the first phase
are scanned in the spiral way and store in a 1-D
array.
2. The array elements are scanned in linear fashion and
elements are stored in a 2-D array same as the
image size
3. The elements are scanned from the 2-D array
linearly and stored in a final array in the spiral way
to generate final encoded image.
(c)
(d)
Decoding by Appling Spiral Scanning:
Second Phase Decoding:
4. Final encoded image is scanned in the spiral way
and stored in a 1-D array.
5. The array elements are scanned in linear fashion
and elements are stored in a 2-D array same as
the image size
6. The elements are scanned from the 2-D array
linearly and stored in an array in the spiral way to
get back the first phase decoded image
(e)
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(f)
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International Journal of Engineering Trends and Technology- Volume2Issue3- 2011
Decoding by Appling Walsh Table:
TABLE II
Correlation
(Original image vs. Recovered image)
1
Table II shows that Correlation between Original image
and recovered image is 1 stating that the proposed method is
lossless.
(g)
(h)
Figure 5.(a)Original Secret image (b)Walsh table Encoded image (c)Walsh
table Encoded image (d) Encoded image by Spiral Scanning (e) Encoded
image by Spiral Scanning(f) Decoded image by Spiral Scanning(g) Decoded
image by Spiral Scanning(h) Recovered image
VI. CONCLUSION
In the proposed method the image is encoded twice which
can be embedded in a cover image for the purpose of image
hiding. Proposed approach is more secured than any single
level encoding technique and reduces the security threat.
REFERENCES
1.
2.
(i)
(j)
Figure 6. (i)Histogram of Original image (j) Histogram of removed image.
3.
4.
Correlation coefficient:
The similarity of Original image A and encoded images B
was measured by the standard correlation coefficient as
follows:
Corr2 computes the correlation coefficient using
6.
∑ ∑ (Amn - A) (Bmn - B)
m
5.
7.
0N. F. Johnson and S. Katzenbeisser,” .A survey of
Steganographic techniques”, in S. Katzenbeisser and F. Peticolas
(Eds.): Information Hiding, pp.43-78. Artech House, Norwood,
MA, 2000.
Lou, D. C. and Liu, J. L. 2002. “Steganography Method for Secure
Communications”. Elsevier Science on Computers& Security, 21,
5: 449-460.
J. Fidrich and M. Goljan, .Practical steganalysis of digital imagesstate of the art., Proc. SPIE Photonics West, Vol. 4675, pp. 1-13,
San Jose, California, Jan. 2002.
Color LAR Codec: A Color Image Representation and
Compression Scheme Based on Local Resolution Adjustment and
Self-Extracting Region Representation : Circuits and Systems for
Video Technology, IEEE Transactions on Issue Date: Aug. 2007
Volume: 17 Issue:8
Ali Al-Ataby and Fawzi Al-Naima, “A Modified High Capacity
Image Steganography Technique Based on Wavelet Transform”,
The International Arab Journal of Information Technology, Vol. 7,
No. 4, October 2010
Formal methods in computer-aided design: first international
conference ... By MandayamSrivas, Albert Camilleri
http://en.wikipedia.org/wiki/Walsh_function
n
r=
∑ ∑ (Amn - A) 2 ∑ ∑(Bmn – B) 2
m
Where
n
m
= mean2 (A), and
n
= mean2 (B).
TABLE 1
Correlation
(Original
image Vs.
1st
level
Encoded
image)
1
Correlation
(Original
image Vs.
2nd
level
Encoded
image)
1
Correlation
(Original
image vs.
1st
level
Decoded
image)
1
Correlation
(Original
image Vs.
2nd
level
Decoded
image)
1
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