path: root/crypto/bn256/cloudflare/example_test.go

// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build amd64,!appengine,!gccgo

package bn256

import (
    "crypto/rand"
)

func ExamplePair() {
    // This implements the tripartite Diffie-Hellman algorithm from "A One
    // Round Protocol for Tripartite Diffie-Hellman", A. Joux.
    // http://www.springerlink.com/content/cddc57yyva0hburb/fulltext.pdf

    // Each of three parties, a, b and c, generate a private value.
    a, _ := rand.Int(rand.Reader, Order)
    b, _ := rand.Int(rand.Reader, Order)
    c, _ := rand.Int(rand.Reader, Order)

    // Then each party calculates g₁ and g₂ times their private value.
    pa := new(G1).ScalarBaseMult(a)
    qa := new(G2).ScalarBaseMult(a)

    pb := new(G1).ScalarBaseMult(b)
    qb := new(G2).ScalarBaseMult(b)

    pc := new(G1).ScalarBaseMult(c)
    qc := new(G2).ScalarBaseMult(c)

    // Now each party exchanges its public values with the other two and
    // all parties can calculate the shared key.
    k1 := Pair(pb, qc)
    k1.ScalarMult(k1, a)

    k2 := Pair(pc, qa)
    k2.ScalarMult(k2, b)

    k3 := Pair(pa, qb)
    k3.ScalarMult(k3, c)

    // k1, k2 and k3 will all be equal.
}