passphrase generation

main.rs

#![feature(iter_intersperse)]

use rand::prelude::*;

use std::fs::File;
use std::io::{BufRead, BufReader};

fn main() {
    // import words list
    let file = File::open("atoms.txt").unwrap();
    let file = BufReader::new(file);

    // collect words into list
    let words = file
        .lines()
        .map(|s| s.unwrap())
        .filter(|s| s.len() > 0)
        .collect::<Vec<String>>();

    // get passphrase len as 1st argument
    let passphrase_len = std::env::args()
        .nth(1)
        .and_then(|s| s.parse::<usize>().ok())
        .unwrap_or(4);

    // select words from list
    let passphrase = words
        .iter()
        .choose_multiple(&mut rand::thread_rng(), passphrase_len)
        .into_iter()
        .map(|s| &**s)
        .intersperse(" ")
        .collect::<String>();

    println!("new passphrase: {}", passphrase);

    // calculate entropy using:
    // E = L (words) * log2(R (word count))
    let entropy_bits = (passphrase_len as f64) * (words.len() as f64).log2();
    println!("entropy: {}", entropy_bits);

    // time to guess (at 1000 guesses/sec)
    // T = E / 1000
    println!("{:.1} years at 1000 guesses/sec", ((2.0f64).powf(entropy_bits) / 1000.) / 60. / 60. / 24. / 365.);
}