Generate a secure 128-bit hexadecimal key

gistfile1.js

/*
Generates a secure random 128-bit hexadecimal key
e.g. "a1ddeb99-14fcd49b-9b5e8e7f-e901bca0"
*/
function generateRandomKey(seed) {

	var key = "";

	if (window.crypto) {
		var key32 = new Uint32Array(4);
		key32 = window.crypto.getRandomValues(key32);
		// Can't array.reduce() on typed arrays, unfortunately.
		/*
		replace the for loop below with:
		var keySegment = 0;
		while (key += key32[keySegment].toString(16), keySegment++ < key32.length) key+= "-";
		*/
		for (keySegment = 0; keySegment < key32.length; keySegment++) { 
			key += (keySegment > 0) ? "-" : ""; // Add delimiter
			key += key32[keySegment].toString(16); // Convert int to hex
		}
	} 

	// Proper RNG is unsupported, so make a key with provider's seed
	else if (seed) {
		//
		// key = best-effort seeded PRNG key
		//
	} 

	// Proper RNG is unsupported, and provider hasn't given us a seed yet
	else {
		key = false;
	}

	return key;

}


/*
Try to load saved key, else generate a new one
*/
function securityKey(seed) {

	var key = $.cookie("bthack_key");

	// Key is unset or invalid; create a new one
	if (key.length !== 8*4+3) {
		key = generateRandomKey(seed);
		$.cookie("bthack_key", key, { expires: 365 });
	}

	return key;

}