IRJET- A Novel Hybrid Security System for OFDM-PON using Highly Improved RC6 Algorithm and Scrambling

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 04 | Apr 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 163
A Novel Hybrid Security system for OFDM-PON using Highly Improved
RC6 Algorithm and Scrambling
Rensu Elsa Chacko1, Sruthi Maria Abraham2, Hari s3
1PG Scholar, Dept. of ECE, Mount Zion College of Engineering, Kadammanitta
2,3Assistant Professor, Dept. of ECE, Mount Zion College of Engineering, Kadammanitta, Kerala, India
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Abstract - This paper proposes a scheme for security
enhancement in the orthogonal frequency division
multiplexing passive optical network (OFDM-PON) based on
highly Improved RC6 algorithm and scrambling technique.
Here the data stream is scrambled and then performs the
highly improved RC6 algorithm to make the data encryption
more secure. Scrambling using morlet wavelet method is
efficient for altering the data in the spatial domain without
losing the data. The highly improved RC6 algorithm is the
modified version of the improved RC6 algorithmwhich ismore
beneficial and secure for the encryption process. By using
scrambling along with the highly improved rc6 algorithm,
encryption security standard will improve without any extra
module with low complexity. Usage of MIMO-OFDM and SIC
makes this system more attractive. We are also testing this
system with the LTE communication system. After decryption,
the signal loss is compensated by the signal enhancement at
the receiver end.
Key Words: Orthogonal FrequencyDivisionMultiplexing
(OFDM), Highly Improved Rivest Cipher6 (hirc6)
algorithm, Walsh Hadamard Transform
1. INTRODUCTION
To meet the demands of next generation networks
in optical communication systems,theorthogonal frequency
division multiplexing passive optical network (OFDM-PON)
[1] has introduced because of its spectral efficiency,
flexibility and relatively high signal transmission capability
[2]. Also communication security is becoming a great
requirement in our society. Since the processes like
encryption, decryption and authentication protocols are
available, increasing security in transmission level is also a
vital concern. Digital chaos algorithms [3] and analog chaos
algorithms [4] are used at the physical layer to increase the
security level of OFDM-PON systems. Noise like
characteristics and sensitivitytoinitial parametersmade the
chaos algorithm more efficient for data transmission in a
highly secure manner.
Pseudo random characteristics, huge parameter
space [5], [6] and good compatibility with the digital signal
processing technology make thedigital chaosalgorithmvery
suitable nowadays. Chaotic scrambling [7], [8], [9], chaotic
constellation manipulation [10] and chaos IQ encryption
techniques [11] are proposed and implemented in several
papers. In chaotic coding, the QAM symbols are rotated in
the constellation and its phases are changed,andatthesame
time the symbol to carrier or symbol to time mappings are
not interrupted. In modern schemes, the iteration processis
done by using floating point algorithm with high
computational precision. The main disadvantage of the
floating point algorithm includes its computational
complexity and hence calculation speedislimited.Soseveral
OFDM frames uses same chaotic sequences, which reduces
the security.
The RC6 algorithm [12] is a secure block cipher
algorithm which was a final candidate project in the AES
(Advanced Encryption Standard)projectoftheUnitedStates
and NESSIE (New European Schemes for Signatures,
Integrity, and Encryption) project of Europe. The block
cipher is classified into Feistel structure and SPN
(Substitution Permutation Network) [13]-[14]. Fiestel
structure uses the same algorithm between encryption and
decryption whereas the SPN uses different algorithm
between encryption and decryption. Therefore the SPN
structure uses twice the area than Fiestel structure when
implemented via hardware. The RC6 algorithm has a
modified Fiestel structure and uses different algorithm
between encryption and decryption. Thus it uses double
space for implementation on hardware. So an improved
version of RC6 is introduced which uses the same structure
for encryption and decryption. The improved RC6
encryption algorithm is implemented by using a symmetric
layer between encryption and decryption process. The
symmetric layer is inserted by using simple rotation and
XOR operations. Here the half of the whole algorithm
performs encryption process and the rest performs
decryption and in between these two the symmetric layer is
introduced.
This paper introduces a highly improved RC6
(HIRC6) algorithm which increases the security of our
system. Data integrity is the main concern in our modern
world. Thus improving efficient RC6 algorithm makes our
encryption standard security more efficient without using
any extra module with low complexity. Here we are
improving the algorithm by creating more security for two
registers A and C and thus making it more efficient and
secure. This paper also uses a technique called scrambling
based on Morlet Wavelet transform for the secure
transmission of data in OFDM-PON. The dynamical
degradation problemisrenovatedbyintroducingthenatural

impermanence of the data. Secure transmission of the
encrypted OFDM signal isexperimentallydemonstrated. The
low implementation complexity and high security
performance necessities are considered here.
2. PRINCIPLE
The principle of this system is to first scramble the
data using morlet wavelet and then do highly improved RC6
(HIRC6) encryption algorithm for high security.
Implementing the two techniques together gives two tier
security for our system. After scrambling operation the data
is once encrypted and then doing encryption algorithm in
this scrambled data makes our system double secure. Here,
we are using an interleaver forincreasingtherandomnature
of our key which is used in the HIRC6 encryption technique.
MIMO-OFDM and a Signal to Interference Canceller (SIC) is
used which makes this system more efficient than the
previous works.
The scrambling technique using morlet wavelet
method is shown in the figure 1. The morlet wavelet splits
the incoming data into two frequency domain as high
frequency component and low frequency component by
passing it through a high pass filter and a low pass filter.
Then these are separately down sampled to reduce its size
and then take the low frequency signals since it contains
more number of information than high frequency. Then
these low frequency signals are then shuffled using Walsh
Hadamard transform. The walsh hadamard transform is a
non sinusoidal, orthogonal transformationtechnique, which
is used to scramble the data withoutanyloss.Thusthedata is
encrypted once.
(a)
(b)
Figure: 1. (a) Scrambling based on morlet wavelet
transform. (b) Reconstruction of the scrambled signal
The HIRC6 encryption and decryption algorithms
are given below. Thus this scrambleddata isagainencrypted
by using HIRC6 encryption technique. The scrambleddata is
stored in four registers named A, B, C and D and then
performs the encryption. RC6 algorithm is symbolically
presented as RC6-w/r/b in whichwmeansthewordsize(32
bits), r denotes the number of rounds and b denotes the
number of key (16 byte).
Six basic operations in RC6 are as follows:
1. a + b integer addition modulo 2W
2. a - b integer subtraction modulo 2W
3. a ⊕ b bitwise exclusive-or of w-bit words
4. a X b integer multiplication modulo 2W
5. a<< >>b rotate the w-bit word a to the left by the
amount given by the least significant lg w bits of b
6. a>><<b rotate the w-bit word a to the right by the
amount given by the least significant lg w bits of b
HIRC6 Encryption Algorithm
B = B + S [0]
D = D + S [1]
for i = 1 to r do
t = (B X (2B + 1)) <<< lg w
u = (D X (2D + 1)) <<< lg w
A = ((A ⊕ t) <<< u) + S [2i]
A1 = ((A ⊕ t) <<< u) + S [2i]
A2= ((A ⊕ t) <<<u) + S [2i]
A=(A1+A2)/2
C = ((C ⊕ u) <<< t) + S [2i+ 1]

C1 = ((C ⊕ u) <<< t) + S [2i+ 1]
C 2= ((C ⊕ u) >>>t) + S [2i+ 1]
C=(C1+C2)/2
end
HIRC6 Decryption Algorithm
C = C – S [2r+3];
A = A – S [2r+2];
for i = r down to 1 do
{
(A, B, C, D) = (D, A, B, C)
u = (D* (2D + 1)) ⋘ lg w
t = (B *(2B + 1)) ⋘ lg w
C = ((C – S [2i+1]) ⋙ t) ⊕ u
A = ((A – S [2i]) ⋙ u) ⊕ t
}
D = D – S [1]
B = B - S[0]
3. BLOCK DIAGRAM
The below figure 2 shows the block diagram of the
system. The key stream generation process is done by C
program and the encryption and decryption process is done
by offline MATLAB.
Figure 2: Block diagram of the system
In the block diagram, the input data is first
scrambled using the morlet wavelet method. This includes
walsh hadamard transform which is a non-sinusoidal,
orthogonal transformation technique which makes the
source data as a perturbed data for reducing the dynamical
degradation problem. Then this scrambleddata isencrypted
by using the highly improved RC6 algorithm which makes
the data secure. Encrypting data after scrambling process
makes this system more resistant to eavesdroppers. Then it
is transmitted using MIMO-OFDM, which has greatest
spectral efficiency and thus delivers highest capacity and
data throughput. It is transmitted through Rayleighchannel,
which is a frequency varying channel that reduces channel
noise and thus data can be decrypted easily. A combiner is
used to combine data from the multiple antennas. Signal to
interference canceller [SIC] is added for reducing
interference at the receiver and can be used to reduce the
effects of noises in the transmitted and received data.
4. RESULT
The experimental result is shown in figure 3. It
shows the bit error rate (BER), symbol error rate (SER) and
theory error rate. This result shows the performance of the
system and here the BER and SER is small enough to show
better performance of our system. Here, both the bit error
rate and symbol error rate should be low when the signal to
noise ratio increases. The black color line shows the
theoretical value. The bit error rate is used to find the error
between the received bits and original transmitted bits. The
symbol error rate is used to find the error between received
distorted symbol andoriginal symbol.Thustheexperimental
result shows that the data encryption and decryption
process are much secure and is well efficient.
Figure 3: The experimental results showing bit error,
symbol error and theory error rates curve with the
improved performance of the system

5. CONCLUSIONS
Here we proposed a secure scheme for OFDM-PON
based on highly improved RC6 encryption and scrambling
with low computational precision. The dynamic generation
of the key stream reduces the strength against attacks.
Meanwhile, the dynamical degradation of the digital chaotic
system is improved by introducing the endemic
impermanence of the data source. The need for low
implementation complexity and high security performance
can be met together. This security upgraded OFDM-PON has
potential applications in secure communications at the
physical layer.
The main work in this paper includes, a technique
scrambling using morlet wavelet is used with highly
improved RC6 encryption algorithm for increasing security.
Thus a two tier security is provided. Here MIMO-OFDM is
used which increases the efficiency of the system. Using an
interleaver instead of a pseudo random binary sequence
[PRBS] generator increases the randomness of the data and
makes it more secure transmission. Frequency varying
channel for transmission is used which reduces the channel
noise and thus the data can decrypted easily. Signal to
interference canceller [SIC] is added for reducing
interference at the receiver and can be used to reduce the
effects of noises in the transmitted and received data.
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