Взлом Vigenere cipher

Скрипты

python

encrypt

def encryption(plaintext, keyword):
    txt_len = len(plaintext)
    keyword *= txt_len // len(keyword) + 1
    keyword = keyword[:txt_len]
    encoded = ""
    for c in range(txt_len):
        newchar = ord(plaintext[c]) + ord(keyword[c]) - 194
        newchar %= 25
        encoded += chr(newchar + 97)
    return encoded

decrypt

def decrypt(key, ciphertext):
    from itertools import cycle
    ALPHA = 'abcdefghijklmnopqrstuvwxyz'
    pairs = zip(ciphertext, cycle(key))
    result = ''
    for pair in pairs:
        total = reduce(lambda x, y: ALPHA.index(x) - ALPHA.index(y), pair)
        result += ALPHA[total % 26]
    return result