private static String getThumbprint(X509Certificate cert)
throws NoSuchAlgorithmException, CertificateEncodingException {
MessageDigest md = MessageDigest.getInstance("SHA-1");
byte[] der = cert.getEncoded();
md.update(der);
byte[] digest = md.digest();
String digestHex = DatatypeConverter.printHexBinary(digest);
return digestHex.toLowerCase();
}