docs: public byte[] signDataWithPrivateKey(byte[] data) throws UnrecoverableKeyException,
                                                       KeyStoreException,
                                                       NoSuchAlgorithmException,
                                                       InvalidKeyException,
                                                       SignatureException {
          if( pvtKeyStore == null ) {
              throw new RuntimeException( "Key store with private key not configured. Please configure it properly before using signed serialization." );
          }
          PrivateKey pvtkey = (PrivateKey) pvtKeyStore.getKey( pvtKeyAlias,
                                                               pvtKeyPassword );
          Signature sig = Signature.getInstance( "MD5withRSA" );
          sig.initSign( pvtkey );
          sig.update( data );
          return sig.sign();
      }