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Generate a random BigNum within the order of the curve using BN_rand_range

pull/93/head
tuxxy 2018-03-19 13:22:41 -06:00
parent fe69a451b3
commit 6e687bbccb
1 changed files with 5 additions and 9 deletions
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14
umbral/bignum.py
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@ -39,17 +39,13 @@ class BigNum(object):
res = backend._lib.EC_GROUP_get_order(group, order, bn_ctx)
backend.openssl_assert(res == 1)
order_int = backend._bn_to_int(order)
# Generate random number on curve
key_size = get_curve_keysize_bytes(curve)
rand_num = int.from_bytes(os.urandom(key_size), 'big')
while rand_num >= order_int or rand_num <= 0:
rand_num = int.from_bytes(os.urandom(key_size), 'big')
new_rand_bn = backend._int_to_bn(rand_num)
new_rand_bn = backend._lib.BN_new()
backend.openssl_assert(new_rand_bn != backend._ffi.NULL)
new_rand_bn = backend._ffi.gc(new_rand_bn, backend._lib.BN_clear_free)
rand_res = backend._lib.BN_rand_range(new_rand_bn, order)
backend.openssl_assert(rand_res == 1)
return cls(new_rand_bn, curve_nid, group, order)
@classmethod