def decrypt_with_cbc_mode(cipher_text: bytes, private_key: bytes,
iv: bytes, encode_g_tilde: bytes) -> bytes:
if not isinstance(private_key, bytes):
raise SDKException(
ErrorCode.other_error(
'the length of private key should be 32 bytes.'))
if len(private_key) != 32:
raise SDKException(
ErrorCode.other_error(
'the length of private key should be 32 bytes.'))
str_g_tilde_x = encode_g_tilde[1:33]
str_g_tilde_y = encode_g_tilde[33:65]
g_tilde_x = string_to_number(str_g_tilde_x)
g_tilde_y = string_to_number(str_g_tilde_y)
g_tilde = Point(NIST256p.curve, g_tilde_x, g_tilde_y, NIST256p.order)
h_tilde = g_tilde * SigningKey.from_string(
string=private_key, curve=NIST256p).privkey.secret_multiplier
seed = b''.join(
[encode_g_tilde,
number_to_string(h_tilde.x(), NIST256p.order)])
aes_key = pbkdf2(seed, 32)
try:
plain_text = AESHandler.aes_cbc_decrypt(cipher_text, iv, aes_key)
except ValueError as e:
raise SDKException(ErrorCode.other_error(e.args[0]))
return plain_text
def decrypt_with_cbc_mode(cipher_text: bytes, private_key: bytes, iv: bytes, encode_g_tilde: bytes) -> bytes:
aes_key = ECIES.generate_decrypt_aes_key(private_key, encode_g_tilde)
try:
plain_text = AESHandler.aes_cbc_decrypt(cipher_text, iv, aes_key)
except ValueError as e:
raise SDKException(ErrorCode.other_error(e.args[0]))
return plain_text
def test_aes_cbc(self):
key = b'Sixteen byte key'
plain_text = b'Attack at dawn'
iv, cipher_text = AESHandler.aes_cbc_encrypt(plain_text, key)
decrypt_out = AESHandler.aes_cbc_decrypt(cipher_text, iv, key)
self.assertEqual(plain_text, decrypt_out)
