Add Joux key agreement example.

examples/joux.rs

@@ -0,0 +1,24 @@
+extern crate bn;
+extern crate rand;
+use bn::{Field, Scalar, G1, G2, pairing};
+
+fn main() {
+    let rng = &mut rand::thread_rng();
+
+    // Generate private keys
+    let alice_sk = Scalar::random(rng);
+    let bob_sk = Scalar::random(rng);
+    let carol_sk = Scalar::random(rng);
+
+    // Generate public keys in G1 and G2
+    let (alice_pk1, alice_pk2) = (G1::one() * &alice_sk, G2::one() * &alice_sk);
+    let (bob_pk1, bob_pk2) = (G1::one() * &bob_sk, G2::one() * &bob_sk);
+    let (carol_pk1, carol_pk2) = (G1::one() * &carol_sk, G2::one() * &carol_sk);
+
+    // Each party computes the shared secret
+    let alice_dh = pairing(&bob_pk1, &carol_pk2) ^ &alice_sk;
+    let bob_dh = pairing(&carol_pk1, &alice_pk2) ^ &bob_sk;
+    let carol_dh = pairing(&alice_pk1, &bob_pk2) ^ &carol_sk;
+
+    assert!(alice_dh == bob_dh && bob_dh == carol_dh);
+}