dannycoates/nonce.html

## nonce.html
<!DOCTYPE html5>
<html>
<body>
<script>
const HMAC_SHA256 = { name: 'HMAC', hash: {name: 'SHA-256'}};
const UTF8 = new TextEncoder('utf-8');
function b64(arrayBuffer) {
  return btoa(String.fromCharCode.apply(null, new Uint8Array(arrayBuffer)))
}

function concatArray(arrays) {
  var size = arrays.reduce((total, a) => total + a.byteLength, 0);
  var index = 0;
  return arrays.reduce((result, a) => {
    result.set(new Uint8Array(a), index);
    index += a.byteLength;
    return result;
  }, new Uint8Array(size));
}

function HMAC(key) {
  return window.crypto.subtle.importKey(
    'raw',
    key,
    HMAC_SHA256,
    false,
    ['sign']
  )
}

async function HMAC_hash(key, input) {
  const hmac = await HMAC(key);
  return window.crypto.subtle.sign('HMAC', hmac, input)
}

async function HKDF_extract(salt, ikm) {
  return HMAC_hash(salt, ikm);
}

async function HDKF_expand(prk, info, l) {
  const input = concatArray([info, new Uint8Array([1])]);
  const h = await HMAC_hash(prk, input);
  return h.slice(0, l);
}

async function HKDF(salt, ikm, info, len) {
  const x = await HKDF_extract(salt, ikm);
  return HKDF_expand(x, info, len);
}

async function go() {
  const key = new Uint8Array([0xde,0xad,0xbe,0xef,0xde,0xad,0xbe,0xef,0xde,0xad,0xbe,0xef,0xde,0xad,0xbe,0xef]);
  const salt = new Uint8Array([1,2,3,4,5,6,1,2,3,4,5,6,1,2,3,4]);

  const prk = await HKDF_extract(salt, key)
  const k = await HDKF_expand(prk, UTF8.encode('Content-Encoding: aes128gcm\0'), 16);
  const nonce = await HDKF_expand(prk, UTF8.encode('Content-Encoding: nonce\0'), 12);
  console.log(b64(k), b64(nonce));
}

go()

</script>
</body>
</html>
	<!DOCTYPE html5>
	<html>
	<body>
	<script>
	const HMAC_SHA256 = { name: 'HMAC', hash: {name: 'SHA-256'}};
	const UTF8 = new TextEncoder('utf-8');
	function b64(arrayBuffer) {
	return btoa(String.fromCharCode.apply(null, new Uint8Array(arrayBuffer)))
	}

	function concatArray(arrays) {
	var size = arrays.reduce((total, a) => total + a.byteLength, 0);
	var index = 0;
	return arrays.reduce((result, a) => {
	result.set(new Uint8Array(a), index);
	index += a.byteLength;
	return result;
	}, new Uint8Array(size));
	}

	function HMAC(key) {
	return window.crypto.subtle.importKey(
	'raw',
	key,
	HMAC_SHA256,
	false,
	['sign']
	)
	}

	async function HMAC_hash(key, input) {
	const hmac = await HMAC(key);
	return window.crypto.subtle.sign('HMAC', hmac, input)
	}

	async function HKDF_extract(salt, ikm) {
	return HMAC_hash(salt, ikm);
	}

	async function HDKF_expand(prk, info, l) {
	const input = concatArray([info, new Uint8Array([1])]);
	const h = await HMAC_hash(prk, input);
	return h.slice(0, l);
	}

	async function HKDF(salt, ikm, info, len) {
	const x = await HKDF_extract(salt, ikm);
	return HKDF_expand(x, info, len);
	}

	async function go() {
	const key = new Uint8Array([0xde,0xad,0xbe,0xef,0xde,0xad,0xbe,0xef,0xde,0xad,0xbe,0xef,0xde,0xad,0xbe,0xef]);
	const salt = new Uint8Array([1,2,3,4,5,6,1,2,3,4,5,6,1,2,3,4]);

	const prk = await HKDF_extract(salt, key)
	const k = await HDKF_expand(prk, UTF8.encode('Content-Encoding: aes128gcm\0'), 16);
	const nonce = await HDKF_expand(prk, UTF8.encode('Content-Encoding: nonce\0'), 12);
	console.log(b64(k), b64(nonce));
	}

	go()

	</script>
	</body>
	</html>