Vigenère Cipher (Python)

Previously I looked at the Vigenère cipher, but I did not have a working Python example. After some thought and consideration I came to the realisation that the Vigenère cipher is pretty much just a Caesar cipher with a shift that changes each letter, which then allowed me to figure out how to make it in Python.

geektechstuff_vigenere_cipher_1 — Vigenere Cipher (Python)

geektechstuff_vigenere_cipher_3 — Vigenere Cipher (Python)

—

#!/usr/bin/python3

# GeekTechStuff

“””

To find out more about the Vigenère Cipher please visit: https://geektechstuff.com/2019/12/25/vigenere-cipher/

“””

def vigenere_enc():

alphabet = “abcdefghijklmnopqrstuvwxyz”

input_string = “”

enc_key = “”

enc_string = “”

# Takes encrpytion key from user

enc_key = input(“Please enter encryption key: “)

enc_key = enc_key.lower()

# Takes string from user

input_string = input(“Please enter a string of text: “)

input_string = input_string.lower()

# Lengths of input_string

string_length = len(input_string)

# Expands the encryption key to make it longer than the inputted string

expanded_key = enc_key

expanded_key_length = len(expanded_key)

while expanded_key_length < string_length:

# Adds another repetition of the encryption key

expanded_key = expanded_key + enc_key

expanded_key_length = len(expanded_key)

key_position = 0

for letter in input_string:

if letter in alphabet:

# cycles through each letter to find it’s numeric position in the alphabet

position = alphabet.find(letter)

# moves along key and finds the characters value

key_character = expanded_key[key_position]

key_character_position = alphabet.find(key_character)

key_position = key_position + 1

# changes the original of the input string character

new_position = position + key_character_position

if new_position > 26:

new_position = new_position – 26

new_character = alphabet[new_position]

enc_string = enc_string + new_character

else:

enc_string = enc_string + letter

return(enc_string)

def vigenere_dec():

alphabet = “abcdefghijklmnopqrstuvwxyz”

input_string = “”

dec_key = “”

dec_string = “”

# Takes encrpytion key from user

dec_key = input(“Please enter encryption key: “)

dec_key = dec_key.lower()

# Takes string from user

input_string = input(“Please enter a string of text: “)

input_string = input_string.lower()

# Lengths of input_string

string_length = len(input_string)

# Expands the encryption key to make it longer than the inputted string

expanded_key = dec_key

expanded_key_length = len(expanded_key)

while expanded_key_length < string_length:

# Adds another repetition of the encryption key

expanded_key = expanded_key + dec_key

expanded_key_length = len(expanded_key)

key_position = 0

for letter in input_string:

if letter in alphabet:

# cycles through each letter to find it’s numeric position in the alphabet

position = alphabet.find(letter)

# moves along key and finds the characters value

key_character = expanded_key[key_position]

key_character_position = alphabet.find(key_character)

key_position = key_position + 1

# changes the original of the input string character

new_position = position – key_character_position

if new_position > 26:

new_position = new_position + 26

new_character = alphabet[new_position]

dec_string = dec_string + new_character

else:

dec_string = dec_string + letter

return(dec_string)

# Testing

print(vigenere_enc())

print(vigenere_dec())

—

I’ve uploaded the full Python program into my Python Encryption GitHub repository: https://github.com/geektechdude/Python_Encryption with file directly at: https://github.com/geektechdude/Python_Encryption/blob/master/geektechstuff_vigenere_cipher.py

Vigenère Cipher (Python)

Related

Published by Geek_Dude

2 thoughts on “Vigenère Cipher (Python)”