Cryptography GUI using python

Using cryptography techniques we can generate keys for a plain text which can not be predicted easily. We use Cryptography to ensure the safe and secure flow of data from one source to another without being accessed by a malicious user.

Prerequisites:

Language used – Python.
Tkinter – This module is used to make GUIs using python language. To know more about tkinter click here.
Basics of Cryptography – Cryptography is used for Secure Communication.

Encryption – The process of encoding a message or information in such a way that only authorized parties can access it.

Decryption – The process of taking encoded or encrypted text or other data and converting it back into text.

Algorithm used

ONE-TIME PAD
The one-time pad is a type of encryption which is unbreakable. A one-time pad will generate a key, this key is shared by both the user so it does encryption as well as decryption. The key used is generated randomly and this key is combined with the plain text in order to form the ciphertext. We can use different algorithms for the generation of the ciphertext such as modular addition, modular XOR, etc. Since the key generated every time is unique, it is impossible to break.

Examples:

In this example, we use a modular addition. Every letter of the message has it’s numerical value associated with it. This numerical value is mapped with the corresponding letter of the key and ciphertext is generated by doing modular addition operation. if the value exceeds 26, the result will be the mod of the value with 26. Here ‘GEEKS’ acts as a plain message and ‘DFSTL’ acts as the one-time pad key.

      G     E      E       K      S      message
   6 (G)   4 (E)  4 (E)   10 (K)  18 (S) message
+  3 (D)   5 (F)  18 (S)  19 (T)  11 (L) key
=  9       9      22      29      29     message + key
=  9 (J)   9 (J)  22 (W)  3 (D)   3 (D) (message + key) mod 26
      J       J       W      D       D  ? ciphertext

Since we used modular addition for the generation of the ciphertext. In order to get back the original message we have to perform modular subtraction. If the value comes out to be negative we will add 26 to the value, the resultant numerical value will result in the generation of the original message.

       J       J       W       D       D  ciphertext
    9 (J)   9 (J)   22 (W)  3 (D)   3 (D) ciphertext
-   3 (D)   5 (F)  18 (S)  19 (T)  11 (L) key
=   6       4       4     -16      -8     ciphertext – key
=   6 (G)   4 (E)  4 (E)  10(K)    18 (S) ciphertext – key (mod 26)
       G       E       E      K       S  ? message

Below is the implementation.

# python module for one-timepad
import onetimepad
# python module to create GUI
from tkinter import *


root = Tk()
root.title("CRYPTOGRAPHY")
root.geometry("800x600")

def encryptMessage():
    pt = e1.get()

    # inbuilt function to encrypt a message
    ct = onetimepad.encrypt(pt, 'random')
    e2.insert(0, ct)

def decryptMessage():
    ct1 = e3.get()

    # inbuilt function to decrypt a message
    pt1 = onetimepad.decrypt(ct1, 'random')
    e4.insert(0, pt1)

# creating labels and positioning them on the grid
label1 = Label(root, text ='plain text')
label1.grid(row = 10, column = 1)
label2 = Label(root, text ='encrypted text')
label2.grid(row = 11, column = 1)
l3 = Label(root, text ="cipher text")
l3.grid(row = 10, column = 10)
l4 = Label(root, text ="decrypted text")
l4.grid(row = 11, column = 10)

# creating entries and positioning them on the grid
e1 = Entry(root)
e1.grid(row = 10, column = 2)
e2 = Entry(root)
e2.grid(row = 11, column = 2)
e3 = Entry(root)
e3.grid(row = 10, column = 11)
e4 = Entry(root)
e4.grid(row = 11, column = 11)

# creating encryption button to produce the output
ent = Button(root, text = "encrypt", bg ="red", fg ="white", command = encryptMessage)
ent.grid(row = 13, column = 2)

# creating decryption button to produce the output
b2 = Button(root, text = "decrypt", bg ="green", fg ="white", command = decryptMessage)
b2.grid(row = 13, column = 11)


root.mainloop()

Output
For encryption:

For decryption:

Note: The default technique used by the module is not as same in the example given. We can apply different formulas for the generation of the ciphertext, however, the underlying principle remains the same.