    if (err == MP_OKAY) {
        err = ecc_mul2add(mG, u1, mQ, u2, mG, curve->Af, curve->prime,
                                                                     key->heap);
    }
    if (err == MP_OKAY) {
        err = ecc_mul2add(mG, u1, mQ, u2, mG, curve->Af, curve->prime,
                                                                     key->heap);
    }