Question

Using Python, write a simple application that takes user input of plaintext and key, and encrypt the plaintext with Vigenere Cipher. The application should then print out the plaintext and the ciphertext.

Answer 1

Note: The program is properly commented, if face any doubt leave a comment.

Program:

#Note: Use only capital letter

#Function to perform Vignere cipher conversion
def vignere_cipher(plain_text, key):
    
    #defining cipher_text variable to store variable
    cipher_text = ""
    
    #storing length of the key to l
    l = len(key)
    
    #we'll iterate through each character of the plain text
    for i in range(len(plain_text)):
        
        #Formula: Ci = (Pi + Ki) mod 26
        #Ci is the cipher text character's ASCII value
        #Pi is the plain text character's ASCII value
        #Ki is the corresponding key character's ASCII value
        
        x = (ord(plain_text[i]) + ord(key[i%l])) % 26
        x += ord('A')
        cipher_text += chr(x)
        
    #returning cipher text
    return cipher_text

#Calling the main program
plain_text = input('Enter plain text: ')
key = input('Enter key: ')
cipher_text = vignere_cipher(plain_text, key)
print('\n\nCipher text: ', cipher_text)

Output:

Leave a comment if face any doubt!! Happy coding!!