def get_order_from_curve(cls, curve: ec.EllipticCurve=None):
"""
Returns the order from the given curve as a CurveBN.
"""
curve = curve if curve is not None else default_curve()
try:
curve_nid = backend._elliptic_curve_to_nid(curve)
except AttributeError:
# Presume that the user passed in the curve_nid
curve_nid = curve
group = openssl._get_ec_group_by_curve_nid(curve_nid)
order = openssl._get_ec_order_by_curve_nid(curve_nid)
return CurveBN(order, curve_nid, group, order)
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)