Vigenerova sifra

# Pouziva sa kniznica itertools a jej funkcia product na generovanie vsetkych moznosti (variacii) / chceme poznat vsetky kluce
from itertools import product

# Zasifrovana sprava (cast z nej, mozes nahradit za cely text)
cipher_text = 'RSX ZRTOGM AQ MYWGHYHIAY DI RNETEN FKJIV.'

# Pomocna funkcia na detekciu ci ide o male pismenko
def is_upper_case(char):
    return 65 <= char and char <= 90

# Obdobne ci ide o velke pismenko
def is_lower_case(char):
    return 97 <= char and char <= 122

# Ide o pismeno vobec?
def is_letter(char):
    return is_upper_case(char) or is_lower_case(char)

# Sifrovanie pomocou vigenerovej sifry (aj desifrovanie, kedze sifra pracuje rovnako iba kluc sa "preklapa")
def crypt(input_text, key):
    output_text = ''
    z = 0
    for index in range(0, len(input_text)):
        c = ord(input_text[index])
        output_character = ''
        if (is_upper_case(c)):
            output_character = chr((c - 65 + key[z % len(key)]) % 26 + 65)
            z += 1
        elif (is_lower_case(c)):
            output_character = chr((c - 97 + key[z % len(key)]) % 26 + 97)
            z += 1
        else:
            output_character = chr(c)

        output_text += output_character

    return output_text

# Ziskanie numerickych hodnot kluca
def filter_key(key):
    result = []
    for index in range(0, len(key)):
        c = ord(key[index])
        if (is_letter(c)):
            result.append((c - 65) % 32)

    return result

# Vypis do konzoly a suboru "vystup.txt", ak chces pustit druhy a treti krat, zmaz tento subor "vystup.txt" najprv
def vypis(text):
    print(text)
    with open('vystup.txt', 'a') as my_file:
        my_file.write(text + '\n')
        my_file.close()

# Mozne pismenka v kluci
ALPHABET = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']

# Dlzka kluca
KEY_LENGTH = 5

# Ziskanie vsetkych variacii (moznych klucov)
POSSIBLE_KEYS = [''.join(i) for i in product(ALPHABET, repeat = KEY_LENGTH)]

# Dekodovanie pomocou klucov
for key in POSSIBLE_KEYS:

    transformed_key = filter_key(key)
    for i in range(0, len(transformed_key)):
        transformed_key[i] = 26 - transformed_key[i] % 26

    vypis('Key: ' + key)
    vypis("Decoded: " + crypt(cipher_text, transformed_key) + '\n')