public BigInteger getPrivateKey(String keyFileName) throws FileNotFoundException, IOException{
			File f=new File(keyFileName);
			FileInputStream fis=new FileInputStream(f);
			ObjectInputStream ois =   new ObjectInputStream(fis);
			  try {
			     n = (BigInteger) ois.readObject();
			    BigInteger e = (BigInteger) ois.readObject();
			  return e;
			  } catch (Exception e) {
			    throw new RuntimeException("Spurious serialisation error", e);
			  } finally{
				if(ois != null){
				ois.close();
				if(fis != null){
					fis.close();
				}}
			}
		}