Novel Algorithm For Encryption:Hybrid of Transposition and Substitution Method

Short Paper
ACEEE Int. J. on Network Security , Vol. 4, No. 1, July 2013

Novel Algorithm For Encryption:Hybrid of Transposition and Substitution Method
Suman Mor1, Anurag Dagar2, Swati Saini2
1

2

SES,BPSMV/CSE, Sonipat, India. Email: suman.mor507@gmail.com
SES,BPSMV/CSE, Sonipat, India. Email: {angelannu30, sheetu38}@gmail.com
II. PROPOSED ALGORITHM

Abstract— This paper presents an algorithm which is hybrib of
Transposition and Substitution method.The main advantage
of this approach is ,it doesn’t use any key from outside because
key is present within the original message.Due to this the
main problem of exchanging keys securely is solved.Both Transposition and Substitution method have their own limitations.So
we use both these method so that the resultant cipher is more
secure and strong.

A. Encryption
1. First we take a message(plain text) from the user which
which he want to encrypt.
2. Take the first character of message and convert it into
its corresponding ASCII code(decimal form),named
Ach.
Double that decimal code means find out 2*Ach.
Find out the corresponding character from ASCII
table and extended ASCII table (any alphabet,digit
or any symbol) and replace original character with
this new character
3. Repeat step 2 for each alphabet or digit number present
in the original message,except blank space.
4. Find out the new converted message using step 2 and
step 3.
5. Find the value of P i.e. the character which present
maximum time in the new converted message.
If there are two characters having same occurance
then select that character which is having large
ASCII code value in decimal form.
6. Calculate Q=int(P) i.e. ASCII code of P in decimal form
7. Perform R=Q % 9;
8. if(R>2 && R<9) then perform K=R
elseif(R==1||R==2||R==3)
then perform K=R+3;
9. Form the group of ‘K’ characters of step 4’s output
including space,alphabets,digits,or any other special
symbol.
10. Reverse characters of each group.
11. Finally we get our secure cipher.

IndexTerms— transposition, substitution, cipher, key, encryption, decryption

I. INTRODUCTION
Since last one decade,it’s a big challenge to send
confidential data or information from one system to another
system. There is a massive growth in internet and
communication technologies in last decade that makes it
difficult to send data securely.When a person is sending
data to another person over the internet then there are lots of
chances of attacks.There is a big challenge to transmit data
over internet with confidentiality and integrity.To provide
confidentiality,we need to encrypt data.[4]So network
security and cryptography are the emerging area where
people are trying to develop various new encryption
algorithms in order to provide more secure data.
Cryptography is an art and science for converting a plain
text into nonreadable cipher text.[2]Cryptography is of two
types:1)private key cryptography:a single key is used for
encryption as well as decryption process.2)public key
cryptography:two keys are used,one for encryption purpose
and other for decryption.These types have advantages as
well as disadvantages.These both types are key based and
the key value can be of any type,any order and any size.[3]
In this paper,we are purposing an encryption method
which works on a block of data.Block size can be changed
for more secure cipher.Block size depends upon the key
value which depends on data because key is hidden in message itself.[1]Transposition method permute the message to
provide security and substitution method places some other
data on the place of message.To provide more secure and
strong cipher we use the hybrid of these techniques.In this
paper we are designing an encryption algorithm which
doesn’t depends on any key and uses transposition as well
as substitution method.

© 2013 ACEEE
DOI: 01.IJNS.4.1. 2

B.Decryption
This is the reverse of encryption process.This process is
done on receiver side.
1.
Find out the character of cipher text which occurs
maximum time i.e. named A
 If there are two characters having same occurance
then select that character which is having large ASCII
decimal value.
2. Find out A’s corresponding ASCII decimal code i.e.B
3. Calculate C=B%9;
4. if(C>2 && C<9) then perform K=C
elseif(C==1||C==2||C==3) then perform K=C+3;
5. Make the group of ‘K’ characters of cipher text.
6. Reverse characters of each group.
40

Short Paper
dbpn bpppÄöÉp Z% jpÿ¿dr
character “p” present maximum time,A=”p”
2. B=112 i.e. p’s corresponding ASCII code
3. Calculate C=B%9
C=112%9=4
4. if(4>2 && 4<8)
(True && true)=true
So K=4
5 Make group of ‘K’characters i.e. 4 characters:
dbpn bpp pÄöÉ p Z% j pÿ¿d r
6 Reverse each group:
npbd ppb ÉöÄp jZ% p d¿ÿp r
7.
After performing step 7, we get output which is
shown below in Table 2 :

7. Perform following steps corresponding each character
of cipher text
 find out the ASCII code of each character.
 Half the ASCII decimal code’s value.
Place the particular character from the ASCII table
corresponding that new half code.
8. Finally we get the original plain text.
III. IMPLEMENTATION

A. Encryption
1) Suppose the original message is
7812881 HJG85d 82TL8H
2) This Table 1 shown below shows the output of step 2:
TABLE 1:REPRESENTS

THE OUTPUT OF STEP

2

OF

TABLE 2:REPRESENTS

ENCRYPTION

7
8
1
2
8
8
1
H
J
G
8
5
D
8
2
T
L
8
H

3)
4)
5)
6)
7)
8)

9)

10)
11)

AS CII
code
(A ch)
55
56
49
50
56
56
49
72
74
71
56
53
100
56
50
84
76
56
72

2*Ach

C ipher
text:

Cipher
text:

110
112
98
100
112
112
98
144
148
142
112
106
200
112
100
168
152
112
114

n
p
b
d
p
p
b
É
ö
Ä
p
j
+
p
d
¿
ÿ
p
r

N
P
B
D
P
P
B
É
Ö
Ä
P
J
+
P
D
¿
Ÿ
P
R

Apply step 2 to all characters of plain text except
blank spaces,finally we get this table.
Now cipher text is:
npbdppb ÉöÄpjZ% pd¿ÿpr
In this converted text character “p” present max.
time so value of P =”p”.
Calculate Q=112(ASCII code of “p”)
R=Q%9 i.e. 112%9
So R=4
if(4>2 && 4<8)
(true&& true)=true
Perform K=4
Grouping of characters according to the value of K
i.e. 4
npbd ppb ÉöÄp jZ% p d¿ÿp r
Now reverse each group:
dbpn bpp pÄöÉ p Z% j pÿ¿d r
Finally cipher text is:
dbpn bpppÄöÉp Z% jpÿ¿dr

OF

DECRYPTION

ASCII
code
(Ach)
110
112
98
100
112
112
98
144
148
142
112
106
200
112
100
168
152
112
114

Ach/2(ha lf
of the
code)
55
56
49
50
56
56
49
72
74
71
56
53
100
56
50
84
76
56
72

plain
text:
7
8
1
2
8
8
1
H
J
G
8
5
d
8
2
T
L
8
H

8. Finally we get our original message
III. ADVANTAGES
This new algorithm has various advantages over already
existing various transposition and substitution methods.
1. It provide limiting range for generation of keys i.e 3 to
8.
2. It doesn’t allow key value 0,1 or 2.
3. There are less chances of Brute force attack because
probability value of attack is low.
4. It provide the encryption of alphabets,digits and special
characters.
5. In this algorithm we use mod function(%9),so it gives
only a limiting range.
6. Final cipher is combination of alphabets,digits,special
symbols and extended special symbol,so to attempt an
attack is very hard or practically difficult to achieve.
7. The main advantage is that,this algorithm is not based
upon a single key.There is no need of sending key to
receiver because key is present within the original text.
8. Easy to decrypt the cipher to get original text.

B. Decryption:
1. Find out the character which present maximum times
in the cipher text
© 2013 ACEEE
DOI: 01.IJNS.4.1. 2

7

A LGOR ITHM

A LGOR ITHM
P lain
text:

THE OUTPUT OF STEP

41

Short Paper
9. In this we change characters with any other characters
including alphabets,digits,special symbol and extended
ASCII code symbol so that if in case attacker find the
code then he couldn’t get any meaningful code.
10. As this algorithm is based on the original text so every
time we get other key value.This provide a strong
encrypted message.

In this algorithm we don’t use any key from outside.Key
is hidden within the message so no need of exchanging
keys.And we use both the method to encrypt data results in
a very strong and secure cipher.
REFERENCES
[1] “Transposition method for cryptography” by Satish Bansal
and Rajesh Shrivastava in „The IUP Journal of Computer
Sciences, Vol. V, No. 4, 2011 .
[2] Atul Kahate (2009), Cryptography and Network Security,
2nd edition, McGraw-Hill.
[3] Stallings W (1999), Cryptography and Network Security,
2nd edition, Prentice Hall.
[4] William Stallings (2003), Cryptography and Network Security,
3rd edition, Pearson Education

V. LIMITATION



This is complex method to encrypt message because of
its implementation.
Use of special symbols and extended ASCII code symbol
makes it complex.
VI. CONCLUSION

This is a hybrid approach of transposition and
substitution method.Both of these approach has their
limitations.Transposition only permutes the data and
substitution places some other character at original
character.Both of these approaches use keys.Exchanging of
key is the main problem.

© 2013 ACEEE
DOI: 01.IJNS.4.1. 2

42

Novel Algorithm For Encryption:Hybrid of Transposition and Substitution Method

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Novel Algorithm For Encryption:Hybrid of Transposition and Substitution Method