class SimpleSubstitution:
def __init__(self):
self.p_alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
self.decrypting = False
def cipher_alphabet(self, password):
''' (str) -> str
Retorna um alfabeto cifrado iniciado com
o texto da palavra chave password
'''
c_alphabet = []
password = password.upper()
for ch in password:
if ch not in c_alphabet:
c_alphabet.append(ch)
idx = self.p_alphabet.find(ch)
p_alphabet = self.p_alphabet[idx:] + self.p_alphabet[:idx]
for ch in p_alphabet:
if ch not in c_alphabet:
c_alphabet.append(ch)
return ''.join(c_alphabet)
def encrypt(self, plaintext, password):
'''(str, str) -> str
Retorna o texto plano cifrado com a cifra de
substituicao com a palavra chave password
'''
txt = ''
p_alphabet = self.p_alphabet
text = plaintext.replace(' ', '').upper()
cipher = self.cipher_alphabet(password)
if self.decrypting:
p_alphabet, cipher = cipher, p_alphabet
self.decrypting = False
for ch in text:
txt += cipher[p_alphabet.find(ch)]
return txt
def decrypt(self, ciphertext, password):
'''(str, str) -> str
Retorna o texto cifrado decifrado com a cifra de
substituicao com a palavra chave password
'''
self.decrypting = True
return self.encrypt(ciphertext, password)
