static void EccPoint_mult(uECC_word_t * result,
                          const uECC_word_t * point,
                          const uECC_word_t * scalar,
                          const uECC_word_t * initial_Z,
                          bitcount_t num_bits,
                          uECC_Curve curve) {
    /* R0 and R1 */
    uECC_word_t Rx[2][uECC_MAX_WORDS];
    uECC_word_t Ry[2][uECC_MAX_WORDS];
    uECC_word_t z[uECC_MAX_WORDS];
    bitcount_t i;
    uECC_word_t nb;
    wordcount_t num_words = curve->num_words;

    uECC_vli_set(Rx[1], point, num_words);
    uECC_vli_set(Ry[1], point + num_words, num_words);

    XYcZ_initial_double(Rx[1], Ry[1], Rx[0], Ry[0], initial_Z, curve);

    for (i = num_bits - 2; i > 0; --i) {
        nb = !uECC_vli_testBit(scalar, i);
        XYcZ_addC(Rx[1 - nb], Ry[1 - nb], Rx[nb], Ry[nb], curve);
        XYcZ_add(Rx[nb], Ry[nb], Rx[1 - nb], Ry[1 - nb], curve);
    }

    nb = !uECC_vli_testBit(scalar, 0);
    XYcZ_addC(Rx[1 - nb], Ry[1 - nb], Rx[nb], Ry[nb], curve);

    /* Find final 1/Z value. */
    uECC_vli_modSub(z, Rx[1], Rx[0], curve->p, num_words); /* X1 - X0 */
    uECC_vli_modMult_fast(z, z, Ry[1 - nb], curve);               /* Yb * (X1 - X0) */
    uECC_vli_modMult_fast(z, z, point, curve);                    /* xP * Yb * (X1 - X0) */
    uECC_vli_modInv(z, z, curve->p, num_words);            /* 1 / (xP * Yb * (X1 - X0)) */
    /* yP / (xP * Yb * (X1 - X0)) */
    uECC_vli_modMult_fast(z, z, point + num_words, curve);
    uECC_vli_modMult_fast(z, z, Rx[1 - nb], curve); /* Xb * yP / (xP * Yb * (X1 - X0)) */
    /* End 1/Z calculation */

    XYcZ_add(Rx[nb], Ry[nb], Rx[1 - nb], Ry[1 - nb], curve);
    apply_z(Rx[0], Ry[0], z, curve);

    uECC_vli_set(result, Rx[0], num_words);
    uECC_vli_set(result + num_words, Ry[0], num_words);
}
static void EccPoint_mult(uECC_word_t * result,
                          const uECC_word_t * point,
                          const uECC_word_t * scalar,
                          const uECC_word_t * initial_Z,
                          bitcount_t num_bits,
                          uECC_Curve curve) {
     
    uECC_word_t Rx[2][uECC_MAX_WORDS];
    uECC_word_t Ry[2][uECC_MAX_WORDS];
    uECC_word_t z[uECC_MAX_WORDS];
    bitcount_t i;
    uECC_word_t nb;
    wordcount_t num_words = curve->num_words;

    uECC_vli_set(Rx[1], point, num_words);
    uECC_vli_set(Ry[1], point + num_words, num_words);

    XYcZ_initial_double(Rx[1], Ry[1], Rx[0], Ry[0], initial_Z, curve);

    for (i = num_bits - 2; i > 0; --i) {
        nb = !uECC_vli_testBit(scalar, i);
        XYcZ_addC(Rx[1 - nb], Ry[1 - nb], Rx[nb], Ry[nb], curve);
        XYcZ_add(Rx[nb], Ry[nb], Rx[1 - nb], Ry[1 - nb], curve);
    }

    nb = !uECC_vli_testBit(scalar, 0);
    XYcZ_addC(Rx[1 - nb], Ry[1 - nb], Rx[nb], Ry[nb], curve);

     
    uECC_vli_modSub(z, Rx[1], Rx[0], curve->p, num_words);  
    uECC_vli_modMult_fast(z, z, Ry[1 - nb], curve);                
    uECC_vli_modMult_fast(z, z, point, curve);                     
    uECC_vli_modInv(z, z, curve->p, num_words);             
     
    uECC_vli_modMult_fast(z, z, point + num_words, curve);
    uECC_vli_modMult_fast(z, z, Rx[1 - nb], curve);  
     

    XYcZ_add(Rx[nb], Ry[nb], Rx[1 - nb], Ry[1 - nb], curve);
    apply_z(Rx[0], Ry[0], z, curve);

    uECC_vli_set(result, Rx[0], num_words);
    uECC_vli_set(result + num_words, Ry[0], num_words);
}