vigenere_cipher.py

"""
    encrypt and decrypt Vigenere Cipher
    Author: Sadip Giri (sadipgiri@bennington.edu)
    Date: 31th Oct. 2018
"""

from cryptography_algebra import convert_sentence_to_np_array_of_numbers, convert_np_array_numbers_to_sentence, maintain_length_of_keyword_with_plaintext
# from genetic_algorithm import run_genetic_algorithm

def encrypt(plaintext, keyword):
    """
        convert plaintext to numpy array of numbers
        increase the length of keyword to maintain same size with plaintext and convert to numpy arrays
        use Vigenere encryption function 
        return cipher text after converting numpy numbers to alphabets
    """
    plaintext_in_numbers = convert_sentence_to_np_array_of_numbers(plaintext)
    extended_keyword = maintain_length_of_keyword_with_plaintext(plaintext, keyword)
    keyword_in_numbers = convert_sentence_to_np_array_of_numbers(extended_keyword)
    encrypt_vigenere_cipher = (plaintext_in_numbers + keyword_in_numbers) % 26
    return convert_np_array_numbers_to_sentence(encrypt_vigenere_cipher).upper()

def decrypt(ciphertext, keyword):
    """
        convert ciphertext to numbers
        extend keyword to maintain same length with ciphertext
        use Vigenere decryption function
        return plain text after converting numpy numbers to alphabets
    """
    ciphertext_in_numbers = convert_sentence_to_np_array_of_numbers(ciphertext)
    extended_keyword = maintain_length_of_keyword_with_plaintext(ciphertext, keyword)
    keyword_in_numbers = convert_sentence_to_np_array_of_numbers(extended_keyword)
    decrypt_vigenere_cipher = (ciphertext_in_numbers - keyword_in_numbers) % 26
    return convert_np_array_numbers_to_sentence(decrypt_vigenere_cipher)

# def crack(ciphertext, keylength, number_of_generations):
#     return run_genetic_algorithm(keylength, number_of_generations, ciphertext, mutation_rate=0.2)

if __name__ == '__main__':
    # print(encrypt("dCode Vigenere automatically", "KEY"))
    # print(decrypt(encrypt("dCode Vigenere automatically", "KEY"), "KEY"))
    # text1 = "Hi I am Sadip Giri from Bennignton College. I am working on cryptanalysis of Vigenere cipher using Genetic Algorithm which is very interesting heuristic approach."
    # keyword = "crypto"
    # keyword = "web"
    # keyword = "cryptography"
    keyword = "sadipgiriisgoodperson"
    txt = "A model of evolution also needs a child insertion method. If the population is to remain the same size, a creature must be removed to make a place for each child. There are several such methods. One is to place the children in the population at random, replacing anyone. This is called random replacement."
    print(encrypt(txt,"ft"))