BN_usub
ret = BN_usub(r, a, b);
ret = BN_usub(r, b, a);
ret = BN_usub(r, a, b);
ret = BN_usub(r, b, a);
if (!BN_usub(rem, rem, D))
if (!BN_usub(B, B, A))
if (!BN_usub(A, A, B))
if (!BN_usub(ret, ret, &(mont->N)))
if (!BN_usub(r, m, b))
if (!BN_usub(r, r, &(recp->N)))
&& !BN_usub(z, z, q))
if (!BN_usub(y, group->field, y))
return BN_usub(point->Y, group->field, point->Y);
int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b);
|| !TEST_true(BN_usub(ret, sum, a))
|| !TEST_true(BN_usub(ret, sum, b))
|| !TEST_true(BN_usub(ret, ret, a))
|| !TEST_true(BN_usub(ret, sum, ret))
|| !TEST_true(BN_usub(ret, ret, b))
|| !TEST_true(BN_usub(ret, sum, ret))