Fast vector commitments

vc.rs

extern crate curve25519_dalek;
extern crate rand;

use curve25519_dalek::constants;
use curve25519_dalek::traits::MultiscalarMul;
use curve25519_dalek::scalar::Scalar;

use curve25519_dalek::edwards::EdwardsPoint;
use curve25519_dalek::edwards::VartimeEdwardsPrecomputation;
use curve25519_dalek::traits::VartimePrecomputedMultiscalarMul;


use std::time::Instant;

use rand::thread_rng;

fn construct_scalars(n: usize) -> Vec<Scalar> {
    let mut rng = thread_rng();
    (0..n).map(|_| Scalar::random(&mut rng)).collect()
}

fn construct_points(n: usize) -> Vec<EdwardsPoint> {
    let mut rng = thread_rng();
    (0..n)
        .map(|_| &Scalar::random(&mut rng) * &constants::ED25519_BASEPOINT_TABLE)
        .collect()
}

fn main() {
    // Some points
    let bases = construct_points(100);
    let precomp = VartimeEdwardsPrecomputation::new(&bases);

    // A1 = a*P + b*Q + c*R
    // let before = Instant::now();
    // let A1 = EdwardsPoint::multiscalar_mul(&scalars, &bases);
    // println!("Elapsed time: {:.2?}", before.elapsed());
    // Note: (&scalars).into_iter(): Iterator<Item=&Scalar>

    // Some scalars
    let scalars = construct_scalars(100);
    let before = Instant::now();
    let A3 = precomp.vartime_multiscalar_mul(&scalars);
    println!("Elapsed time: {:.2?}", before.elapsed());

    // A2 = (-a)*P + (-b)*Q + (-c)*R
    // let minus_abc = scalars.iter().map(|x| -x);
    // let A2 = EdwardsPoint::multiscalar_mul(minus_abc, &bases);
    // Note: minus_abc.into_iter(): Iterator<Item=Scalar>

    // assert_eq!(A1.compress(), (A3).compress());
    // println!("Success!");
}