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Encryption of text characters using ASCII values


Call for Papers Engineering Journal, May 2019

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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.[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.

    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]

    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.

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