nadachat/js/rsaworker.js

simple secure chat with end to end encyption

var window=self; // fools sjcl into thinking we are running in a browser scope instead of a worker scope

// this is now injected as a string to avoid net io / log entries:
// importScripts('https://nadachat.com/js/sjcl-core.js'); //make with directions on https://github.com/bitwiseshiftleft/sjcl/wiki/Getting-Started, adding --with-ecc to configure as the only change, then taking core.js

// over-ride ajcl AES defaults with stronger values:
sjcl.json.defaults.ks=256;
sjcl.json.defaults.ts=128;

// add entropy to the fortuna instance used by sjcl:
sjcl.random.addEntropy(STAMP); // use entropy from PHP and DOM
sjcl.random.addEntropy(stamp());  // use as much local entropy as possible
sjcl.random.addEntropy(Math.random().toString(2).split("").filter(/./.test, /01/).length); // mostly because it does a ms or two of work to spin following timers
sjcl.random.addEntropy(getRandomFromCrypto(94)); // use OS=provided values, munged with timing data
sjcl.random.addEntropy(location.href); // use blob url for unpredictable values 
sjcl.random.addEntropy(timeserial()+timeserial()); // yet more timing data



// sends a response or error back to the web app:
function send(type, data){
	self.postMessage({type:type, data: data});
}




self.addEventListener("message", function(evt) {

	sjcl.random.addEntropy(stamp());
	
	var e = evt.data;
	if(e.data && e.data.STAMP)	sjcl.random.addEntropy(e.data.STAMP); // used if passing in more late-gathered entopy (like motion data)

	
	if(e.type == "ecc") { // generate a new ecc curve keypair
		var pair = sjcl.ecc.elGamal.generateKeys(sjcl.ecc.curves.c521); // a fresh ecc key pair
		send("ecc", {  // serialize into shippable values:
			pubx:  pair.pub.get().x,
			puby:  pair.pub.get().y,
			sec: pair.sec.get()
		});	
	}//end if ecc?

	
	if(e.type == "encode") { // encode using ECC public key
		try {
			var pub=e.pub.split ? JSON.parse(e.pub) : e.pub,
			curve = sjcl.ecc.curves.c521,
			point = new sjcl.ecc.point(sjcl.ecc.curves.c521, curve.field.fromBits(pub.x), curve.field.fromBits(pub.y)),
			pubK = new sjcl.ecc.elGamal.publicKey(sjcl.ecc.curves.c521, point),
			plain = [].slice.call(new TextEncoder().encode(JSON.stringify(e.data))),
			encrypted = sjcl.encrypt(pubK, plain);				
			send("encode", (""+encrypted));
		} catch(y) {
			send("error", y+"");
		}
	}//end if encode?
	
	
	if(e.type == "decode") { // decode using ECC secret key
		try {		
			var sec = new sjcl.ecc.elGamal.secretKey(
				sjcl.ecc.curves.c521,  
				sjcl.ecc.curves.c521.field.fromBits( e.ob.sec )
			),			
			decodedArray = sjcl.decrypt(sec, e.data, {raw: 1});
			send("decode", new TextDecoder().decode(new Uint8Array(decodedArray)));
		} catch(y) {
			send("error", y+"");
		}
	}//end if decode?
		

	if(e.type == "aesenc") { // encode using AES (GCM)
		try {
			var pw=sjcl.codec.hex.toBits(e.key);
			var enc=sjcl.encrypt(pw, e.data, {mode : "gcm"});
			send("enc", enc);
		} catch(y) {
			send("error", y.message);
		}
	}//end if encode?
	

	if(e.type == "aesdec") {// decode using AES (GCM)
		try {			
			var key=sjcl.codec.hex.toBits(e.key),
			plain=sjcl.decrypt(key, e.data);
			send("dec", plain);
		} catch(y) {
			send("error", y.message);
		}
	}//end if dec?
	
	
});//end onmessage() event handler



// utility functions

function stamp(){ // returns a bunch of random digits each time it's called
  function random(n) {return [].slice.call(crypto.getRandomValues(new Uint32Array(n)));}
  return [
    Math.random(), 
    Math.floor(performance.now()*100), 
    (Date.now()-147298194451)/(location.href.match(/\d/g).length), 
    random(1)[0]
  ].join("").replace(/\D/g,"").replace(/^0+|0+$/g,""); 
}


// crypto - OS-provided CSPRNG with timing data mixin - sync and fast
function getRandomFromCrypto(chars) { 
    var format="int";
	chars=Math.floor(chars/1.5);
	var pad=(""+Array(Math.max(64,Math.floor(chars/9.75)))).split("").map(stamp),
	out =  [].slice.call(crypto.getRandomValues(new Int16Array(chars)))
	.map(Math.abs)
	.filter(function(a,b,c){ return a<100; });
	out = out.map(function(a,b,c){
             var padSlot=Math.floor(b/10), padCol=b%10;
             return ("00"+(a+(+pad[padSlot][padCol]||1)).toString().slice(-2)).slice(-2);
        }).join("");

	
	return out.slice(-chars);
} //end getRandomFromCrypto()


// a sync timestamp method, returns a new 10-digit string each time
function timeserial() {
	return(Date.now() / (performance.now() * 100)).toString().split("").filter(/./.test, /\d/).slice(-10).join("");
};