hashcash rust

hashcash.rs

extern crate sha3;
extern crate num_bigint;
extern crate num_traits;
use num_bigint::{BigUint, ToBigUint};
use sha3::{Digest, Sha3_256};


fn sha3(data: &Vec) -> [u8; 32] {
    let mut hasher = Sha3_256::new();
    hasher.input(data);
    let r = hasher.result();
    let mut ret = [0u8; 32];
    for i in 0..32 {
        ret[i] = r[i];
    }
    ret
}

pub fn genpow(data: Vec, difficulty: &BigUint) -> ([u8; 32], u32) {
    let mut nonce = 0u32;
    let mut input = data.clone();
    while BigUint::from_bytes_be(&sha3(&input)) >= *difficulty {
        nonce += 1;
        input = data.clone();
        input.append(&mut nonce.to_be_bytes().to_vec());
    }
    return (sha3(&input), nonce)
}

pub fn verify(data: Vec, pow: [u8; 32], nonce: u32, difficulty: &BigUint) -> bool {
    let mut input = data.clone();
    input.append(&mut nonce.to_be_bytes().to_vec());
    return BigUint::from_bytes_be(&sha3(&input)) < *difficulty;
}

fn main() {
    // 2^240
    let mut difficulty: BigUint = BigUint::parse_bytes(b"1766847064778384329583297500742918515827483896875618958121606201292619776", 10).unwrap();
    println!("difficulty set to {}", difficulty);
    println!("generating pow...");
    let (pow, nonce) = genpow(vec![1, 2, 3, 4, 5], &difficulty);
    println!("got it! {:x?}", pow);
    println!("verification: {}", verify(vec![1,2,3,4,5], pow, nonce, &difficulty));
}