protected void engineinitsign(privatekey privatekey) throws invalidkeyexception {
    cipherparameters param = rsautil.generateprivatekeyparameter((rsaprivatekey) privatekey);

    signer.init(true, param);
  }
  protected void engineinitverify(publickey publickey) throws invalidkeyexception {
    cipherparameters param = rsautil.generatepublickeyparameter((rsapublickey) publickey);

    signer.init(false, param);
  }