bn_expand
BIGNUM *bn_expand(BIGNUM *a, int bits);
if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
if (bn_expand(Ri, (int)sizeof(BN_ULONG) * 2) == NULL)
if (bn_expand(ret, i * 4) == NULL)
if (bn_expand(ret, i * 4) == NULL)