def hash(cls, *crypto_items, params: UmbralParameters) -> 'CurveBN':
# TODO: Clean this in an upcoming cleanup of pyUmbral
blake2b = hashes.Hash(hashes.BLAKE2b(64), backend=backend)
for item in crypto_items:
try:
item_bytes = item.to_bytes()
except AttributeError:
if isinstance(item, bytes):
item_bytes = item
else:
raise TypeError(
"{} is not acceptable type, received {}".format(
item, type(item)))
blake2b.update(item_bytes)
hash_digest = openssl._bytes_to_bn(blake2b.finalize())
_1 = backend._lib.BN_value_one()
order_minus_1 = openssl._get_new_BN()
res = backend._lib.BN_sub(order_minus_1, params.curve.order, _1)
backend.openssl_assert(res == 1)
bignum = openssl._get_new_BN()
with backend._tmp_bn_ctx() as bn_ctx:
res = backend._lib.BN_mod(bignum, hash_digest, order_minus_1,
bn_ctx)
backend.openssl_assert(res == 1)
res = backend._lib.BN_add(bignum, bignum, _1)
backend.openssl_assert(res == 1)
return cls(bignum, params.curve)
def from_bytes(cls, data: bytes, curve: Optional[Curve] = None) -> 'CurveBN':
"""
Returns a CurveBN object from the given byte data that's within the size
of the provided curve's order.
By default, the underlying OpenSSL BIGNUM has BN_FLG_CONSTTIME set for
constant time operations.
"""
curve = curve if curve is not None else default_curve()
size = backend._lib.BN_num_bytes(curve.order)
if len(data) != size:
raise ValueError("Expected {} B for CurveBNs".format(size))
bignum = openssl._bytes_to_bn(data)
return cls(bignum, curve)
def hash_to_curvebn(*crypto_items,
params: UmbralParameters,
customization_string: bytes = b'',
hash_class: Type[Hash] = Blake2b) -> CurveBN:
customization_string = b'hash_to_curvebn' + customization_string
hash_function = hash_class(customization_string=customization_string)
for item in crypto_items:
try:
item_bytes = item.to_bytes()
except AttributeError:
if isinstance(item, bytes):
item_bytes = item
else:
raise TypeError("Input with type {} not accepted".format(
type(item)))
hash_function.update(item_bytes)
hash_digest = openssl._bytes_to_bn(hash_function.finalize())
one = backend._lib.BN_value_one()
order_minus_1 = openssl._get_new_BN()
res = backend._lib.BN_sub(order_minus_1, params.curve.order, one)
backend.openssl_assert(res == 1)
bignum = openssl._get_new_BN()
with backend._tmp_bn_ctx() as bn_ctx:
res = backend._lib.BN_mod(bignum, hash_digest, order_minus_1, bn_ctx)
backend.openssl_assert(res == 1)
res = backend._lib.BN_add(bignum, bignum, one)
backend.openssl_assert(res == 1)
return CurveBN(bignum, params.curve)