 Open Access
 Total Downloads : 5
 Authors : Akanksha Mathur, Arshi Riyaz, Jyoti Vyas
 Paper ID : IJERTCONV2IS03032
 Volume & Issue : ETRASCT – 2014 (Volume 2 – Issue 03)
 Published (First Online): 30072018
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Encryption of text characters using ASCII values
Encryption of text characters using ASCII values
Akanksha Mathur Gujarat University Ahmedabad, India akanmamthur@gmail.com
Arshi Riyaz
Department of Computer Science and Engineering JIET Universe, Jodhpur, India arshiriyaz@gmail.com
Jyoti Vyas
Department of Computer Science and Engineering JIET Universe, Jodhpur, India jyotivyas@jietjodhpur.com
AbstractThis paper is demonstrating the encryption and decryption of text characters using their ASCII values. This is a kind of symmetric Encryption algorithm in which same key is used for both encryption and decryption purpose.
KeywordsASCII, encryption, Decryption, ciphertext, plaintext, cryptographic algorithm

A cryptographic algorithm is a mathematical functions and unchanging set of steps to perform encryption and decryption of the original data. These algorithms work in combination with a secret key which can be a combination of alphabets, numbers, words or phrases. For the purpose of encryption, the algorithm combines the original data or the text to be encoded (plaintext which is input to the encryption process) with the secret key supplied for the encryption. This combination will yield a ciphertext (which is our desired code or we can say output). Similarly, for the purpose of decryption, the algorithm combines the encrypted data or ciphertext with may or may not be the same secret key and this combination will yield again the same plaintext. If there is any modification takes place in any of the secret key or the plaintext, the algorithm will yield a different result than before. The main objective of every cryptographic algorithm is to make it as difficult as possible to decrypt the generated ciphertext without using the key. If a really good cryptographic algorithm is used, then there is no technique significantly better than methodically trying every possible combination of key.


Introduction
This algorithm is used to encrypt data by using ASCII values of the data to be encrypted. The secret key used will be modified to another string and that string is used as a key to encrypt or decrypt the data.[3] So, it can be said that it is a
kind of symmetric encryption algorithm. In symmetric encryption algorithm, only one key is used for both encryption and decryption process. The key is transmitted to both the sender and receiver before the process of encryption and decryption. So, the secret key plays an important role and its strength depends on the length of key (in bits). The longer the length of key is, it is harder to break it and shorter the length of key is it is even easier to break it. [1] Thus it violates the security purpose of encryption. Similarly .it uses same key for encryption and decryption but by slightly modifying it.
The main limitation of this algorithm is that it will operates when the length of input and the length of key are same. That is, if the length of input is 3 then the length of key must be 3 neither less or nor more than 3.

Algorithm for encryprion process

Start

Input the string (can include numbers, alphabets and special symbols) from the user. This string is known as the plain text to be encrypted.

Get the ASCII values of each character of plain text and store them in an array asciicontent.

Find out the minimum value min from the array asciicontent. This min value is used further in the algorithm.

For I = 1 to n where n is the length of the input of the plain text
modcontent[I] = asciicontent[I] % min
If the value of mod content is greater than 16, then again perform modcontent %16, and record the places where changes occur or record the positions in record array where the value of mod content is greater than 16.

Input the string (can include numbers, alphabets and special symbols) from the user. This string is the key which is used to encrypt the plain text.\

Get the ASCII values of each character of key and store them in an array asciikey.

For I = 1 to n where n is the length of the input of the key modkey[I] = asciikey[I] % min

Take the binary values of each value of modkey.

Perform the right circular shifts of binary values n times (where n is the length of input i.e. plain text) and save them in binary array.

Add min value to each ASCII value of each character of encrypt key after shifting.
Encryptkey[I]=ASCII (Binary[I]) + min Encryptkey is the final key which is used to encrypt the plain text.

To encrypt the original data (input) or plaintext to generate ciphertext, add each mod content value to the ASCII values of final encrypt key.

Ciphertext[I]=ASCII(Excryptley[I])+modcontent[I Convert the ASCII values into their corresponding characters to get the cipher text.


Algorithm for decryption purpose

Start

Get the ASCII values of each character of cipher text in
asciicipher.

Find out the minimum from ASCII values of each character of cipher text.

Subtract ASCII values of final encrypt key from asciicipher
Difference[I]=asciicipher[I]ASCII(Encryptkey[I]) Add 16 to the stored positions from record array where the modcontent value is greater than 16.

Add minimum to each value of difference to generate plaintext.


Here, representing some of the examples of encryption and decryption process of varying length of input (or key) say 2, 3, 4, 5.

Example 1: Input Length: 2
Let Plain text is: – am Key is: – ab
TABLE 1. EXAMPLE 1
Encryptkey (After adding min)
101
97
Encryptkey
e
a
ASCII(Excryptley)+modcontent
101
109
Ciphertext
e
m
DECRYPTION
Cipher
e
m
ASCIICipher
101
109
minimum=101
asciifinalencryptkey
101
97
difference
0
12
asciiplain
97
109
plaintext`
a
m
Execution time: 320ms.

Example 2: Input Length: – 3
Let Plain text=bcf Key=cbc
ENCRYPTION
Input (Plain Text)
b
c
f
asciicontent
98
99
102
min=98
modcontent
0
1
4
Key
c
b
c
asciikey
99
98
99
modkey
1
0
1
binary
0001
0000
0001
Right Circular Shifts (3 times)
Shift 1
1000
1000
0000
Shift2
0100
0100
0000
Shift 3
0010
0010
0000
Encryptkey
2
2
0
Encryptkey (After adding min)
100
100
98
Encryptkey
d
d
b
ASCII(Excryptley)+modcontent
100
101
102
Ciphertext
d
e
f
DECRYPTION
TABLE 2. EXAMPLE 2.
ENCRYPTION
Input (Plain Text)
a
m
asciicontent
97
109
min=97
modcontent
0
12
Key
a
b
asciikey
97
98
modkey
0
1
binary
0000
0001
Right Circular Shifts (2 times)
Shift 1
1000
0000
Shift 2
0100
0000
Encryptkey
4
0
Cipher
d
e
f
Difference
13
4
7
0
ASCIICipher
100
101
1
02
Asciiplain
110
101
104
97
minimum=100
plaintext`
n
e
h
a
asciifinalencryptkey
100
100
98.
imated Time: 3679 ms.
Example 4:Inuput Length: 5
plaintext= pacgl Key=abcde
difference
0
1
4Est
asciiplain
98
99
10D2 .
plaintext`
b
c
fLet
Execution Time: 2098ms.

Example 3: Input Length: – 4
Let Plain Text= neha Key= abcd
TABLE 3. EXAMPLE 3
ENCRYPTION
Input (Plain Text)
p
a
c
g
l
asciicontent
112
97
99
103
108
min=97
modcontent
15
0
2
6
11
Key
a
b
c
d
e
asciikey
97
98
99
100
101
modkey
0
1
2
3
4
binary
0000
0001
0010
0011
0100
Right Circular Shifts (5 times)
Shift 1
0000
0000
1001
0001
1010
Shift 2
0000
0000
0100
1000
1101
Shift 3
1000
0000
0010
0100
0110
Shift 4
0100
0000
0001
0010
0011
Shift 5
1010
0000
0000
1001
0001
Encryptkey
10
0
0
9
1
Encryptkey
(After adding min)
107
97
97
106
98
Encryptkey
k
a
a
j
b
ASCII(Excryptley)+
modcontent
122
97
99
112
109
Ciphertext
z
a
c
p
m
DECRYPTION
Cipher
z
a
c
p
m
ASCIICipher
122
97
99
112
109
minimum=97
Asciifinal
encryptkey
107
97
97
106
98
difference
15
0
2
6
11
asciiplain
112
97
99
103
108
plaintext`
p
a
c
g
l
TABLE 4. EXAMPLE 4
ENCRYPTION
Input (Plain Text)
n
e
h
a
asciicontent
110
101
104
97
min=97
Modcontent
13
4
7
0
Key
a
b
c
d
Asciikey
97
98
99
100
Modkey
0
1
2
3
Binary
0000
0001
0010
0011
Right Circular Shifts (4 times)
Shift 1
1000
0000
1001
0001
Shift 2
1100
0000
0100
1000
Shift 3
0110
0000
0010
0100
Shift 4
0011
0000
0001
0010
Encryptkey
3
0
1
2
Encryptkey (After
adding min)
100
97
98
99
Encryptkey
d
a
b
c
ASCII(Excryptley)+
modcontent
113
<>101 105
99
Ciphertext
q
e
i
c
DECRYPTION
Cipher
q
e
i
c
ASCIICipher
113
101
105
99
minimum=99
Asciifinalencryptkey
100
97
98
99
Execution Time:: 3780ms.


The proposed algorithm has the following limitations:

More Execution time

Key Length and length of plain text must be same.[3]

If it is applied on any file then the length of key is equal to the length of file which is not considered as good


In the future wok related to proposed algorithm, the limitations of proposed algorithm are overcome by

Encrypting and decrypting data with may or may not be same key length size in comparison with input size.

Appling on files of different length

Applied on images


Gurjeevan Singh, Ashwani Kumar Singla, K.S. Sandha, Throughput Analysis of Various Encryption Algorithms, International Journal of Computer Science and Technology, Vol. 2, Issue 3, Septemver 2011.

Diaa Salama Abd Elminaam, Hatem Mohamed Abdual Kader, and Mohiy Mohamed Hadhoud, Evaluating the Performance of Symmetric Encryption Algorithms, International Journal of Network Security, Vol.10, No.3, PP.216222, May 2010.
Can you change this algorithm into program? please i need it.. Please response me quickly..