Diffe-Hellman-Merkle Key Exchange Demonstration (using curves crate)

dhm.rs

//! ```cargo
//! [dependencies]
//! rand = "0.3.16"
//! curves = { git = "https://gitlab.com/neucrypt/curves", branch = "release" }
//! ```
extern crate rand;
extern crate curves;
use curves::{Secp, SecpOrd, ECGroup, Ford};

/// This demonstrates the math beneath a Diffe-Hellman-Merkle key exchange, and
/// is not meant to be meaningful in it of itself. Obviously A's and B's code
/// must be separated for this to accomplish anything.
fn key_exchange(g: Secp) -> (Secp, Secp)
{
    // A random value generator, good enough for demonstration purposes.
    let mut rng = rand::thread_rng();

    // A's code.
    let q1 = SecpOrd::rand(&mut rng);
    let a = g.scalar(&q1);

    // B's code.
    let q2 = SecpOrd::rand(&mut rng);
    let b = g.scalar(&q2);

    // A's code, implying that B sent `b` to A.
    let ka = b.scalar(&q1);

    // B's code, implying that A sent `a` to B.
    let kb = a.scalar(&q2);

    // Return both party's normalized (affine?) keys.
    (ka.affine(), kb.affine())
}

fn main() {
    // Generate the generator.
    let g = ECGroup::gen();
    println!("Group generator is:\n      {:?}\n\n", g);

    let (ka, kb) = key_exchange(g);
    assert_eq!(ka, kb);

    println!("Successfully shared key:\n      {:?}", ka);
}