public ECDSASignatureBuilder update(String label, byte[] bytes) {
   if (bytes == null) throw new RuntimeException("Input is null: " + label);
   references.add(label);
   count += bytes.length;
   log(label, bytes);
   digest.update(bytes, 0, bytes.length);
   return this;
 }
 public ECDSASignatureBuilder update(String label, String input) {
   if (input == null) throw new RuntimeException("Input is null: " + label);
   references.add(label);
   byte[] bytes = input.getBytes(Charset.forName("UTF-8"));
   count += bytes.length;
   log(label, bytes);
   digest.update(bytes, 0, bytes.length);
   return this;
 }