class Vegenere:
def __init__(self):
self.helper = Helper()
def encrypt(self, plaintext, key):
plaintext = self.helper.format(plaintext)
key = self.helper.format(key)
kryptotext = ''
for index, char in enumerate(plaintext):
plain_char = ord(char) - 65
key_char = ord(key[index % len(key)]) - 65
krypto_char = ((plain_char + key_char) % 26) + 65
kryptotext += unichr(krypto_char)
return kryptotext
def decrypt(self, kryptotext, key):
kryptotext = self.helper.format(kryptotext)
key = self.helper.format(key)
plaintext = ''
for index, char in enumerate(kryptotext):
krypto_char = ord(char) - 65
key_char = ord(key[index % len(key)]) - 65
plain_char = ((krypto_char - key_char) % 26)
if plain_char < 0:
plain_char += 26
plain_char += 65
plaintext += unichr(plain_char)
return plaintext
def _char_frequency(text):
frequencies = [0 for i in range(26)]
text = Helper.format(text)
for index, char in enumerate(text):
frequencies[ord(char) - 65] += 1
return frequencies
def _find_positions(self, krypto_text):
krypto_text = Helper.format(krypto_text)
positions = {}
for i in range(len(krypto_text)-2):
sub = krypto_text[i:i+3]
if sub in positions:
positions[sub].append(i+1)
else:
positions[sub] = [i+1]
return self._remove_zero_or_one_occurancies(positions)
