Function ecmult_const_mult_xonly

src/secp256k1/src/tests.c:4677–4730

}

static void ecmult_const_mult_xonly(void) {
    int i;

    /* Test correspondence between secp256k1_ecmult_const and secp256k1_ecmult_const_xonly. */
    for (i = 0; i < 2*COUNT; ++i) {
        secp256k1_ge base;
        secp256k1_gej basej, resj;
        secp256k1_fe n, d, resx, v;
        secp256k1_scalar q;
        int res;
        /* Random base point. */
        random_group_element_test(&base);
        /* Random scalar to multiply it with. */
        random_scalar_order_test(&q);
        /* If i is odd, n=d*base.x for random non-zero d */
        if (i & 1) {
            random_fe_non_zero_test(&d);
            secp256k1_fe_mul(&n, &base.x, &d);
        } else {
            n = base.x;
        }
        /* Perform x-only multiplication. */
        res = secp256k1_ecmult_const_xonly(&resx, &n, (i & 1) ? &d : NULL, &q, i & 2);
        CHECK(res);
        /* Perform normal multiplication. */
        secp256k1_gej_set_ge(&basej, &base);
        secp256k1_ecmult(&resj, &basej, &q, NULL);
        /* Check that resj's X coordinate corresponds with resx. */
        secp256k1_fe_sqr(&v, &resj.z);
        secp256k1_fe_mul(&v, &v, &resx);
        CHECK(check_fe_equal(&v, &resj.x));
    }

    /* Test that secp256k1_ecmult_const_xonly correctly rejects X coordinates not on curve. */
    for (i = 0; i < 2*COUNT; ++i) {
        secp256k1_fe x, n, d, r;
        int res;
        secp256k1_scalar q;
        random_scalar_order_test(&q);
        /* Generate random X coordinate not on the curve. */
        do {
            random_fe_test(&x);
        } while (secp256k1_ge_x_on_curve_var(&x));
        /* If i is odd, n=d*x for random non-zero d. */
        if (i & 1) {
            random_fe_non_zero_test(&d);
            secp256k1_fe_mul(&n, &x, &d);
        } else {
            n = x;
        }
        res = secp256k1_ecmult_const_xonly(&r, &n, (i & 1) ? &d : NULL, &q, 0);
        CHECK(res == 0);
    }
}

static void ecmult_const_chain_multiply(void) {
    /* Check known result (randomly generated test problem from sage) */