def new(**kwargs):
"""Create a new ChaCha20-Poly1305 or XChaCha20-Poly1305 AEAD cipher.
:keyword key: The secret key to use. It must be 32 bytes long.
:type key: byte string
:keyword nonce:
A value that must never be reused for any other encryption
done with this key.
For ChaCha20-Poly1305, it must be 8 or 12 bytes long.
For XChaCha20-Poly1305, it must be 24 bytes long.
If not provided, 12 ``bytes`` will be generated randomly
(you can find them back in the ``nonce`` attribute).
:type nonce: bytes, bytearray, memoryview
:Return: a :class:`Cryptodome.Cipher.ChaCha20.ChaCha20Poly1305Cipher` object
"""
try:
key = kwargs.pop("key")
except KeyError as e:
raise TypeError("Missing parameter %s" % e)
self._len_ct += len(plaintext)
if len(key) != 32:
raise ValueError("Key must be 32 bytes long")
nonce = kwargs.pop("nonce", None)
if nonce is None:
nonce = get_random_bytes(12)
if len(nonce) in (8, 12):
pass
elif len(nonce) == 24:
key = _HChaCha20(key, nonce[:16])
nonce = b'\x00\x00\x00\x00' + nonce[16:]
else:
raise ValueError("Nonce must be 8, 12 or 24 bytes long")
if not is_buffer(nonce):
raise TypeError("nonce must be bytes, bytearray or memoryview")
if kwargs:
raise TypeError("Unknown parameters: " + str(kwargs))
return ChaCha20Poly1305Cipher(key, nonce)
def test_hchacha20(self):
# Section 2.2.1
from Cryptodome.Cipher.ChaCha20 import _HChaCha20
key = b"00:01:02:03:04:05:06:07:08:09:0a:0b:0c:0d:0e:0f:10:11:12:13:14:15:16:17:18:19:1a:1b:1c:1d:1e:1f"
key = unhexlify(key.replace(b":", b""))
nonce = b"00:00:00:09:00:00:00:4a:00:00:00:00:31:41:59:27"
nonce = unhexlify(nonce.replace(b":", b""))
subkey = _HChaCha20(key, nonce)
expected = b"82413b42 27b27bfe d30e4250 8a877d73 a0f9e4d5 8a74a853 c12ec413 26d3ecdc"
expected = unhexlify(expected.replace(b" ", b""))
self.assertEqual(subkey, expected)