def test_cannot_set_default_curve_twice():
config = _copy_config_for_testing()
# pyumbral even supports untrustworthy curves!
config.set_default_curve(ec.SECP256R1)
# Our default curve has been set...
assert config.default_curve() == ec.SECP256R1
# ...and used to set the order of our default parameters.
assert config.default_params().order == Point.get_order_from_curve(
ec.SECP256R1)
# ...but once set, you can't set the default curve again, even if you've found a better one.
with pytest.raises(config._CONFIG.UmbralConfigurationError):
config.set_default_curve(ec.SECP256K1)
def __init__(self, curve: ec.EllipticCurve):
from umbral.point import Point, unsafe_hash_to_point
from umbral.utils import get_curve_keysize_bytes
self.curve = curve
self.g = Point.get_generator_from_curve(self.curve)
self.order = Point.get_order_from_curve(self.curve)
g_bytes = self.g.to_bytes(is_compressed=True)
self.CURVE_MINVAL_SHA512 = (1 << 512) % int(self.order)
self.CURVE_KEY_SIZE_BYTES = get_curve_keysize_bytes(self.curve)
parameters_seed = b'NuCypherKMS/UmbralParameters/'
self.u = unsafe_hash_to_point(g_bytes, self, parameters_seed + b'u')