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 __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
curve_nid = backend._elliptic_curve_to_nid(curve)
self.g = Point.get_generator_from_curve(self.curve)
self.order = openssl._get_ec_order_by_curve_nid(curve_nid)
g_bytes = self.g.to_bytes(is_compressed=True)
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')
def hash(cls, *crypto_items, params=None):
params = params if params is not None else default_params()
curve_nid = backend._elliptic_curve_to_nid(params.curve)
order = openssl._get_ec_order_by_curve_nid(curve_nid)
group = openssl._get_ec_group_by_curve_nid(curve_nid)
# 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 = blake2b.finalize()
hash_digest = int.from_bytes(hash_digest,
byteorder='big',
signed=False)
hash_digest = openssl._int_to_bn(hash_digest)
_1 = backend._lib.BN_value_one()
order_minus_1 = openssl._get_new_BN()
res = backend._lib.BN_sub(order_minus_1, 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, curve_nid, group, order)
def from_int(cls, num, curve: ec.EllipticCurve = None):
"""
Returns a CurveBN object from a given integer on a curve.
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()
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)
conv_bn = openssl._int_to_bn(num, curve_nid)
return cls(conv_bn, curve_nid, group, order)
def to_bytes(self, is_compressed=True):
"""
Returns the Point serialized as bytes. It will return a compressed form
if is_compressed is set to True.
"""
affine_x, affine_y = self.to_affine()
# Get size of curve via order
order = openssl._get_ec_order_by_curve_nid(self.curve_nid)
key_size = backend._lib.BN_num_bytes(order)
if is_compressed:
y_bit = (affine_y & 1) + 2
data = int.to_bytes(y_bit, 1, 'big')
data += int.to_bytes(affine_x, key_size, 'big')
else:
data = b'\x04'
data += int.to_bytes(affine_x, key_size, 'big')
data += int.to_bytes(affine_y, key_size, 'big')
return data
def gen_rand(cls, curve: ec.EllipticCurve = None):
"""
Returns a CurveBN object with a cryptographically secure OpenSSL BIGNUM
based on the given curve.
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()
curve_nid = backend._elliptic_curve_to_nid(curve)
group = openssl._get_ec_group_by_curve_nid(curve_nid)
order = openssl._get_ec_order_by_curve_nid(curve_nid)
new_rand_bn = openssl._get_new_BN()
rand_res = backend._lib.BN_rand_range(new_rand_bn, order)
backend.openssl_assert(rand_res == 1)
if not openssl._bn_is_on_curve(new_rand_bn, curve_nid):
new_rand_bn = cls.gen_rand(curve=curve)
return new_rand_bn
return cls(new_rand_bn, curve_nid, group, order)
