# Encryption of text characters using ASCII values DOI : 10.17577/IJERTCONV2IS03032

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#### 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

1. 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.

1. 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. 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.  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.

2. Algorithm for encryprion process

1. Start

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

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

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

5. 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.

6. 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.\

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

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

9. Take the binary values of each value of modkey.

10. 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.

11. 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.

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

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

3. Algorithm for decryption purpose

1. Start

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

asciicipher.

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

4. 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.

5. Add minimum to each value of difference to generate plaintext.

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

1. 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.

2. 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.

3. 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.

3. The proposed algorithm has the following limitations:-

1. More Execution time

2. 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

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

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

2. Appling on files of different length

3. Applied on images

1. 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.

2. 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.

### One thought on “Encryption of text characters using ASCII values”

1. Shakeel says:

Can you change this algorithm into program? please i need it.. Please response me quickly..