def _derive_padding_crypto(self, seed,
pad_string): # XXX consider secret_seed
"""
Derive and return an obfs2 padding key using the pad string in 'pad_string'.
"""
secret = self.mac(pad_string, seed, self.shared_secret)
return aes.AES_CTR_128(secret[:KEYLEN], secret[KEYLEN:])
def _derive_crypto(self, pad_string):
"""
Derive and return an obfs3 key using the pad string in 'pad_string'.
"""
secret = hmac_sha256.hmac_sha256_digest(self.shared_secret, pad_string)
return aes.AES_CTR_128(secret[:KEYLEN], secret[KEYLEN:],
counter_wraparound=True)
def test_encrypt_decrypt_small_ASCII(self):
"""
Validate that decryption and encryption work as intended on a small ASCII string.
"""
self.key = "\xe3\xb0\xc4\x42\x98\xfc\x1c\x14\x9a\xfb\xf4\xc8\x99\x6f\xb9\x24"
self.iv = "\x27\xae\x41\xe4\x64\x9b\x93\x4c\xa4\x95\x99\x1b\x78\x52\xb8\x55"
test_string = "This unittest kills fascists."
cipher1 = aes.AES_CTR_128(self.key, self.iv)
cipher2 = aes.AES_CTR_128(self.key, self.iv)
ct = cipher1.crypt(test_string)
pt = cipher2.crypt(ct)
self.assertEqual(test_string, pt)
def _derive_crypto(self, pad_string): # XXX consider secret_seed
"""
Derive and return an obfs2 key using the pad string in 'pad_string'.
"""
secret = self.mac(pad_string,
self.initiator_seed + self.responder_seed,
self.shared_secret)
return aes.AES_CTR_128(secret[:KEYLEN], secret[KEYLEN:])
