static String appendSignature(OpenPgp openPgp, String xmlText, String keySpecifier) throws IOException { xmlText += "\n"; byte[] xmlData = Charsets.UTF_8.encode(xmlText).array(); String signature = base64().encode(openPgp.sign(xmlData, keySpecifier)); return xmlText + "<!-- Base64 Signature\n" + signature + "\n-->\n"; }