def raw_bytes_from_point(point: Point, only_y_coord=False) -> bytes:
uncompressed_point_bytes = point.to_bytes(is_compressed=False)
if only_y_coord:
y_coord_start = (1 + Point.expected_bytes_length(is_compressed=False)) // 2
return uncompressed_point_bytes[y_coord_start:]
else:
return uncompressed_point_bytes[1:]
def kdf(ecpoint: Point, key_length: int) -> bytes:
data = ecpoint.to_bytes(is_compressed=True)
return HKDF(algorithm=hashes.BLAKE2b(64),
length=key_length,
salt=None,
info=None,
backend=default_backend()).derive(data)
def kdf(
ecpoint: Point,
key_length: int,
salt: Optional[bytes] = None,
info: Optional[bytes] = None,
) -> bytes:
data = ecpoint.to_bytes(is_compressed=True)
hkdf = HKDF(algorithm=hashes.BLAKE2b(64),
length=key_length,
salt=salt,
info=info,
backend=default_backend())
return hkdf.derive(data)
def kdf(
ecpoint: Point,
key_length: int,
salt: Optional[bytes] = None,
info: Optional[bytes] = None,
) -> bytes:
data = ecpoint.to_bytes(is_compressed=True)
salt = salt or b''
info = info or b''
return Hkdf(
salt,
data,
hash=blake2b,
).expand(info=info, length=key_length)