[nodejs][javascript] Diffie-Hellman key exchange by nodejs-0.5

dh-usage.js

// node.js 0.5 Diffie-Hellman example                                           
var assert = require("assert");
var crypto = require("crypto");

// the prime is shared by everyone                                              
var server = crypto.createDiffieHellman(512);
var prime = server.getPrime();


// sharing secret key on a pair                                                 
var alice = crypto.createDiffieHellman(prime);
alice.generateKeys();
var alicePub = alice.getPublicKey();

var bob = crypto.createDiffieHellman(prime);
bob.generateKeys();
var bobPub = bob.getPublicKey();

var bobAliceSecret = bob.computeSecret(alicePub);
var aliceBobSecret = alice.computeSecret(bobPub);

// public keys are different, but secret is common.                             
assert.notEqual(bobPub, alicePub);
assert.equal(bobAliceSecret, aliceBobSecret);
// use common secret as shared encryption key...                                


// shared secret with 3rd person                                                
var carol = crypto.createDiffieHellman(prime);
carol.generateKeys();
var carolPub = carol.getPublicKey();

var carolAliceSecret = carol.computeSecret(alicePub);
var aliceCarolSecret = alice.computeSecret(carolPub);

assert.notEqual(carolPub, alicePub);
assert.equal(carolAliceSecret, aliceCarolSecret);

// secret depends on pairs                                                      
assert.notEqual(aliceBobSecret, aliceCarolSecret);
var carolBobSecret = carol.computeSecret(bobPub);
assert.notEqual(carolAliceSecret, carolBobSecret);