code: public byte[] getPrivKeyBytes33() {
          byte[] bytes33 = new byte[33];
          byte[] priv = getPrivKeyBytes();
          System.arraycopy(priv, 0, bytes33, 33 - priv.length, priv.length);
          return bytes33;
      }
docs: Returns private key bytes, padded with zeros to 33 bytes.
  @throws java.lang.IllegalStateException if the private key bytes are missing.