byte[] bytes = new byte[] { 60, 109, -73, 0, 0,
                            0, 0, -128, -1, -1,
                            -1, -121, 19, 21, 14, 0 };

String base64 = "PG23AAAAAID///+HExUOAA==";

new BigInteger(1, bytes).toString(64)