An Enhanced Encryption Technique using BCD and Bit Complementation

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 01 | Jan -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 896
An Enhanced Encryption Technique using BCD and Bit Complementation
Shashi Gautam1, Shubha Mishra2, Dr. Manish Shrivastava3
1PG Scholar in Information Technology, LNCT Bhopal, M.P, India
2Asst. Professor in Information Technology, LNCT Bhopal, M.P, India
3Professor and Head of Information Technology, LNCT Bhopal, M.P, India
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Abstract - With the advancement of the network technology,
providing data security over internet is the very crucial task.
There are many cryptographic algorithmshavebeenintroduced
to provide data security, but almost all algorithms are costly in
terms of time, memory and computation. The proposed
cryptographic algorithm is based on binary operationsand with
basic CPU computation. This algorithm uses BCD (binary coded
decimal), 1's complement for data encryption and 2's
complement for key encryption. Instead of using key directly in
data encryption, key is encrypted first and then data. There are
two different algorithms are used for key to encrypt data and to
send key. The three level of encryption leaves nothing for
unauthorized decryption. Use of basic binary operations and
basic computation boosts the performance of the algorithms.
The obtained experimental analysis shows that the proposed
algorithm outperforms as comparing with the similar variant
implemented algorithm.
Key Words: BCD, 1's complement, 2's complement, binary
addition/subtraction
1. INTRODUCTION
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Now a day’s transmission of messages (commercial and
confidential/personal) over internet to and fro is the common
in daily life. Sender sends message, thatcan onlybereceivedby
the recipient (authorized) user but there are so many
unauthorized access to this message. Listening of any stream
over internet by unauthorized users is illegal. To secure
messages from unauthorised access mechanism call
cryptography is used. Encryption of message by sender so that
only authorized recipient can decrypt is called cryptography.
Cryptography set the goals of confidentiality, non-repudiation,
integrity and authenticity by exploiting the techniques called
encryption and decryption. Before sending the message, it is
first converted into non-intelligible form by using some
substitution,codingand/oradding redundancies and now this
non-readable message is called cipher text. Use of key to
encrypt messages is one of the very important standards of the
encryption process. The process of gaining original message
from the cipher text is called decryption, which is exactly the
reverse process of the encryption. There are two flavours of
cryptography:
 Asymmetric key cryptography and
 Symmetric key cryptography
Fig 1: Symmetric Encryption
Fig 2: Asymmetric encryption
In asymmetric key cryptography, there is a public key and
private key. Public key is used to encrypt the message which is
available publically. PrivateKey as the namesaysisprivate(i.e.
not to disclose to any one) which is used to decrypt the cipher
text. In symmetric cryptography, there is a single key for both
encryptionand decryption.Thiskeymustbekeptsecret,except
to the sender and intended recipient. So it is mandatory to
transmit the secret key to the intended recipient with the
cipher text but to send secret key with the cipher text, the key
must also be encrypted.

Fig 3: Symmetric encryption
Security of messages in symmetric key cryptography relies
on the secrecy and length of the secret key. Examples of
asymmetric key cryptography are RSA, DSA. Most wide use of
asymmetric key cryptography is in digital signature and
message authentication. DES, Triple DES BLOWFISH, AES are
the examples of symmetrickey cryptography. Most wideuseof
symmetric key cryptography is to provide security for
communication over network. Transport level security (TLS)
uses HMAC algorithm and Internet protocol security (IPSec)
uses HMAC and DES algorithms. Because there is a single key
for encryption and decryption insymmetrickey,thesymmetric
key cryptography is more efficient than the asymmetric key
cryptography. Symmetric key cryptography is almost 100 to
1000 times faster than the asymmetric key and also requires
less memory as comparedtotheasymmetrickeycryptography.
2. LITERATURE SURVEY
LEA (Link Encryption Algorithm) [3] is a stream cipher
algorithm which uses an 8-bit ASCII character coding (i.e. for
key) forencryptionand decryption. To produce theciphertext,
bitwise addition of key with the plain text is conduct. Every
timean encryption initializes, the algorithm is started. Thetow
sequences are combined to form the key sequences. First
sequence has probable long period and the second one is great
complexity. The LEA encryptionalgorithmcanbedividedintoa
driving part and a combining part. The driving part consists of
a set of maximum length Linear Feedback Shift Registers. It
mainly governs the state sequence of the generator and is
responsible for providing sequences of large periods and good
statistics. The combining part is essentiallynonlinear.Ithasthe
task to make thecipherstreamgenerationtobemathematically
complex.
Evaluation of DES, TDES, AES Blowfish and Two fish
Encryption Algorithm [9] based on Space Complexity analyzes
and find an efficient encryption/decryption algorithm which
takes less space among these encryption algorithms such as
DES, TDES, AES, Blowfish and Two fish. The DES requires less
space among these algorithms. DES divides the plaintext into a
block of 64 bits and takes key size of 56 bits, it performs 16
processing round to encrypt plaintext. TDES is the
advancement in the DES which works 3 times than the DES.
Triple DES uses encryption with key k1, then decryption with
key k2, and finally encryption with key k3 and uses 56-bits for
key. These three keys are used, so that it can protect against
brute force attack. Therefore Triple DES requires more space
than DES. Blowfish requires maximum space among these
cryptographic algorithms. Because two fish algorithm is
derived from Blowfish, therefore it requiresalmostsamespace
as the Blowfish.
Evaluation of symmetric encryption algorithms [6]
introduces the drawbacks of symmetric keycryptographyDES
which is a block cipher algorithm. DES is a very strong
algorithm to provide security as its key length and design is
concerned. But because lots of complicated computation,
computation rounds it is slow during implementations. For all
computing systems, DES cannot be exploited. In the
implementation, DEScanbeusedindifferentmodeofblockand
key length and that's why it spends much of the precious time
during encryption and decryption processes, and the
consequences of this is the higher throughputduringpeaktime
of communications. The application of Hybrid encryption
algorithm in software security discussed in [5]. This technique
makes utilization of a key with minimum length of eight byte
(64-bits). This 8 byte key it’s generated randomly by using
some random functions is used to encrypt/decrypt a
plaintext/ciphertext respectively. There are three different
encryption phases, each uses different sub-keys of sizes 128,
192 and 256 bits (variable length keys). This multiphase
encryption techniques require a small space for encryption.
Code substitution, code folding and code permutation are the
threesteppedmethods,whichusesmulti-dimensionalmatrixto
strengthen the complexity of security. As the use of multiple
keys with varyinglengths in different phases of encryption,the
process of encryption get much of security but it also
introduces lots of computational overhead. [4] If
encryption/decryption process includes large amount of
computations, then they must make large use of resources like
CPU time, energy resources (such as battery power), and
memory capacity. In some networks like wireless ad hoc
networks, as there is a need of more power consumption, so it
is required tomakeimprovementsinbatterytechnologysothat
it can give long time power backup. Algorithm presented a
potential management of use of energy in various wireless
devices using symmetric key cryptographic algorithms. The
experiment conducted on 600 encryptions using a 5MB file
with Triple DES, the 45% of the remaining battery energy,
which denied any further encryption. AES is the faster and
efficient than the rest of the cryptographicalgorithms.Withthe
key size of 8bytes, the AES increases the energy consumption
by 8% without any transmission. To reduce the energy
consumption by reducingtheroundsinAESencryptionprocess
leads the encryptions insure.
An optimized encryption technique using an arbitrary
matrix with probabilistic encryption is discussed in [7]. This
technique uses an arbitrary matrix for key generation. This
arbitrary matrix is used for generating multiple key for

encrypting the same data blocks. This technique makes use of
matrix vector multiplication and makes use of some
substitution functions andconversionstogeneratethestreams
of key. This key is used by both encryption and decryption for
each character. The encryption processinputsatextcharacters
(one character at a time), and produce corresponding cipher
character. The same process is used for decrypting the cipher
character but in reverse order. Encrypting character by
character adds more security to the data but repeat same
process for each character requires lot of
encryption/decryption time.
3. PROPOSED WORK
1. The proposed algorithm makes use of 8-bit ASCII, 1's
complement addition/subtraction, 2's complement
addition/subtraction and a 4-bit 8421 encoding.
2. A key used once is not be used again. Also an encrypted
form of key is used for both encryption and decryption.
Also to share a key with recipient, a different algorithm
is used for encryption a key.
3. The encryption function takescompleteplaintextatone
as input to encrypt. Decryption function works in
reverse order of encryption function.
Algorithm for generating key:
Input: a random number r.
Output: an encrypted key F available for plaintext encryption
1. K = (r)2 to 16-bit binary
2. K = k1, k2, k3, k4 // 4-bit binary BCD
3. append all D = Ki, 0<i<=4
4. find digit sum of D until a single digit is generated
5. Final key F is obtained.
Algorithm for sending key:
Input: a random number r.
Output: an encrypted key
1. K = (r)2 to 16-bit binary
2. K = k1, k2, k3, k4 // 4-bit binary BCD
3. find 2's complement of each Ki, 0<i<=4
4. convert it to decimal
5. This four numeric number is then send with the
ciphertext.
Algorithm for encryption:
Input: Plain text P
Output: Cipher text C
1. Let Pi is the plaintext word for i = 1 to 256.
2. Convert each Pi to 8-bit ASCII
3. group each ASCII binary to 4-bits and find BCD
4. Each BCD is then converted to 8-bit binary
5. Take 1's complement of output of step 4 and group it
into 8-bit
6. find equivalent decimal value for each 8-bit character
7. for each word do:
 assign a special unique identifier to key value
 append key to the output
8. Scramble all the encrypted word
9. Cipher text
Algorithm for decryption:
Input: Cipher text C
Output: Plain text P
1. Find the special identifier from the cipher text C to
remove key value.
2. separate all Ci from cipher text for i from 1 to 256
3. For each character of Ci find its 8-bit ASCII and
convert it to binary equivalent.
4. Find 1's complement of each character by reverting
binary value from 0 to 1 and 1 to 0.
5. Remove last 8-bit of each word to find word order
number and descramble them in original order.
6. Make group of 4 bits and find its BCD and then
convert it to decimal and again make group of 8-bit to
find ASCII characters.
7. combine each ASCII to form words
8. Plain text
The encryption algorithm by using encrypted keymakesits
greatly impossible for the unauthorized person to regain the
original text who does not know the encryption key and
algorithm. Even if the algorithm is known, still it is very hard to
regeneratethe samekey withthe samekeyencryptionprocess.
As the encryption of plaintext depends upon the plaintext
therefore for every plaintext, it generates different cipher text.
These algorithms also go to beyond the standard and make the
length of cipher text bigger than that of plaintext. This feature
demonstrates the strengthofthealgorithm.Thuswithinashort
duration, this algorithm generates a strong cipher text.
4. RESULTS ANALYSIS
Implementation details:
Algorithm is implemented using JAVA 1.8 and Windows
Command prompt-bit versions with 2GB RAM to analyse their
performance.
Avalanche effect:
The algorithm is tested over 0 to 255 times which produces
different key every time. The strengthofthealgorithmdepends
on the strength of the key. Therefore it makes difficult for third
party to regain the original message as the key is different
every time. So a small difference in a key has great
consequences on the cipher text, which generates maximum
avalanche effect. It strengthens the algorithm and key
maximally. Hence it is almost superior to other cryptographic
algorithms.
Time complexity
Time complexity of an algorithm is defined as the time
needed to run it to completion. This time is the combination of
compile timeandexecutiontime.Alsothistimeincludessystem
time as well as virtual machine time. Also an algorithm
compiles once can execute several times. Therefore in

complexity analysis, we are only considering execution time
and total required time.
CPU time:
CPU time is the time required to perform cpu operations,
basic ALU operations. According to the obtained experimental
result the cpu time required for encryption and decryption is
very less in proposed algorithm. Figure 4 shows the CPU time
required for encryption and figure 5 shows the time required
for decryption.
Fig 4: CPU time of Encryption in ms
Total time:
Total time includes time required for executing the
algorithm, virtual machine time and user time. Figure 5 show
the total time required for encryption and figure 6 shows the
total time required for decryption.
Total Time = Run Time + VM Time + User Time
Comparison analysis shows that the proposed algorithm
requires very less time for encryption and decryption.
Fig 5: CPU time of Decryption in ms
Memory complexity
Memory complexity is derived from the amount of memory
required by an algorithm in heap section as well as non-heap
section at run time. Figure 5 shows the comparison of amount
of memory requirement for encryption and figure 6 shows the
comparison of amount of memory requirement fordecryption
process.
Fig 6: Total Memory for Encryption in kB
Fig 7: Total Memory for Decryption
Throughput analysis
Throughput can be defined as the proportion of size of data
divided by total time required for the cryptosystem.
Throughput = (Size of Data (D))/(Total Time (T))
Where D is the size of Data in KBs, and T is the total time taken
by cryptosystem in Seconds. Experimental result shows that
the throughput of the proposed algorithm is higher as

compared to its implementedvariant.Theoverall performance
of the two implemented algorithm is summarize in the below
given table. To summarize entire performance of a system we
use some indication such as Low, High, Medium, and Average.
Table 1: Comparison chart between proposed and base
algorithm
Parameters
Proposed Algorithm Base Algorithm
Encryption Decryption Encryption Decryption
CPU Time
(ms)
214.5 233.75 663.5 706.5
Total Time
(ms)
265.25 284.75 781 824
Memory
(kB)
15310.25 15287.25 39351.75 40655.25
5. CONCLUSION
In information streaming technology where the securityofthe
information plays an important role, cryptosystem fulfill this
requirement. In this paper we implementedthesimilarvariant
of the today's encryption system along with the proposed
algorithm and analyzes their performances by considering
several parameters such as CPU time, Total time as a time
complexity and memory as a memory complexity. The
experimental analysis shows that the proposed algorithm is
efficient and performs well for text crypto.
REFERENCES
[1]. Sombir singh, Enhancing the Security of DES Algorithm
Using Transposition Cryptography Techniques, 2013
[2]. Nimmi Gupta, Implementation of Optimized DES
Encryption Algorithm upto 4 Round on Spartan3,
International Journal of Computer Technology and
Electronics Engineering (IJCTEE) Volume 2 , Issue 1,
2012
[3]. Ain Shams Eng J, LEA: Link encryption algorithm
Proposed stream cipher algorithm, 2014
[4]. Evaluation of Symmetric Encryption Algorithms for
MANETs, Dec. 2010 IEEE International Conference on
Computational Intelligence and Computing Research
(ICCIC)
[5]. The Application of Hybrid Encryption Algorithm in
Software Security, Fourth International Conference on
Computational Intelligence and Communication
Networks (CICN), 2012
[6]. Evaluation of Symmetric Encryption Algorithms for
MANETs, Dec. 2010 IEEE International Conference on
Computational Intelligence and Computing Research
(ICCIC)
[7]. An optimized encryption technique using an arbitrary
matrix with probabilistic encryption, Paresh Ratha, 3rd
International Conferenceon RecentTrendsinComputing
2015 (ICRTC-2015)
[8]. Efficient key management and cipher text generation
using BCD coded parity bits, Rahul Ranjan, 3rd
International Conferenceon RecentTrendsinComputing
2015 (ICRTC-2015)
[9]. Evaluation of DES, TDES, AES, Blowfish and Two fish
Encryption Algorithm: Based on Space Complexity, MD
Asif Mushtaque, Harsh Dhiman, Shahnawaz Hussain,
Shivangi Maheshwari, International Journal of
Engineering Research & Technology (IJERT) Vol. 3 Issue
4, April – 2014
[10]. New image encryption combining fractional DCT via
polynomial interpolationwithdependentscramblingand
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An Enhanced Encryption Technique using BCD and Bit Complementation