parseParams.java

private static String parseVals(String key, String val, String prefix) throws InvalidKeyException, NoSuchAlgorithmException, IOException {
  	long ts = System.currentTimeMillis() / 1000;

		String[] parts = val.split("\\|");
		String u_prefix = parts[0];
		String u_b64 = parts[1];
		String u_sig = parts[2];

		String sig = Util.hmacSign(key, u_prefix + "|" + u_b64);
		if (!Util.hmacSign(key, sig).equals(Util.hmacSign(key, u_sig))) {
			return null;
		}

		if (!u_prefix.equals(prefix)) {
			return null;
		}

		byte[] decoded = Base64.decode(u_b64);
		String cookie = new String(decoded);

		String[] cookie_parts = cookie.split("\\|");
		String username = cookie_parts[0];
		String expire = cookie_parts[2];

		long expire_ts = Long.parseLong(expire);
		if (ts >= expire_ts) {
			return null;
		}

		return username;		
	}