OneTimePad

import string

ALPHABET = string.ascii_uppercase


def convert_to_alphabet_indices(word):
    alphabet_indices = list()
    for character in list(word):
        character_index = ALPHABET.index(character)
        alphabet_indices.append(character_index)
    return alphabet_indices


def convert_to_alphabet_letters(indices):
    alphabet_letters = list()
    for index in indices:
        alphabet_letters.append(ALPHABET[index])
    return ''.join(alphabet_letters)


def sum_list_values(first_list, second_list):
    result = list()
    for x, y in zip(first_list, second_list):
        total = x + y
        alphabet_length = len(ALPHABET)
        if total >= alphabet_length:
            total %= alphabet_length
        result.append(total)
    return result


def subtract_list_values(first_list, second_list):
    return [x - y for x, y in zip(first_list, second_list)]


plaintext = "GEHEIMTEXT"
one_time_pad_text = "PADUGSNQHG"

plaintext_indices = convert_to_alphabet_indices(plaintext)
print("Klartext-Indizes:", plaintext_indices)

one_time_pad_text_indices = convert_to_alphabet_indices(one_time_pad_text)
print("OTP-Indizes:", one_time_pad_text_indices)

cyphertext_indices = sum_list_values(plaintext_indices, one_time_pad_text_indices)
print("Geheimtext-Indizes:", cyphertext_indices)

cyphertext = convert_to_alphabet_letters(cyphertext_indices)
print("Geheimtext:", cyphertext)

difference_cyphertext_indices_and_otp_indices = subtract_list_values(cyphertext_indices, one_time_pad_text_indices)
print("Differenz zwischen Geheimtext-Indizes und OTP-Indizes:", difference_cyphertext_indices_and_otp_indices)

encrypted_text = convert_to_alphabet_letters(difference_cyphertext_indices_and_otp_indices)
print("Entschlüsselter Text:", encrypted_text)