调用未定义的方法CI_Encrypt :: sha1（）

I follow a tutorial from youtube Tutorial codeigniter - Insert but, Im getting this error inside my controller file for my browser when im using the encryption library from codeigniter 2.
Error code when using encryption.

$paramUsu['clave'] = $this->encrypt->sha1($this->input->post('txtClave'));

But when im just passing it without the encryption it working just fine.

$paramUsu['clave'] = $this->input->post('txtClave');

Im getting this error at my browser:

Fatal error: Call to undefined method CI_Encrypt::sha1() in C:\xampp\htdocs\TRAINING\tutorialCI\application\controllers\cpersona.php on line 31
A PHP Error was encountered Severity: Error
Message: Call to undefined method CI_Encrypt::sha1()
Filename: controllers/cpersona.php
Line Number: 31
Backtrace:

Here is the code for my controller:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Cpersona extends CI_Controller {

    function __construct()
    {
        parent::__construct();
                //call model
                $this->load->model('mpersona');
                $this->load->model('musuario');
                //call encryption library for password at 'clave' textfield
                $this->load->library('encrypt');
    }

    public function index(){
        $this->load->view('persona/vpersona');
    }

    public function guardar(){
        //persona
        $param['dni'] = $this->input->post('txtDNI');
        $param['nombre'] = $this->input->post('txtNombre');
        $param['appaterno'] = $this->input->post('txtApPaterno');
        $param['apmaterno'] = $this->input->post('txtApMaterno');
        $param['email'] = $this->input->post('txtEmail');
        $param['fecnac'] = $this->input->post('datFecNac');
        //usuario
        $paramUsu['nomUsuario'] = $this->input->post('txtUsuario');
        //$paramUsu['clave'] = $this->input->post('txtClave');
        $paramUsu['clave'] = $this->encrypt->sha1($this->input->post('txtClave'));

        //call function name in model
        //call function variable '$param'
        //$this->mpersona->guardar($param);

        $lastId = $this->mpersona->guardar($param);

        //check if $lastId is filled in persona table
        if ($lastId > 0){
            $paramUsu['idPersona'] = $lastId;
            //$paramUsu value will be go also in usuario model
            $this->musuario->guardarUsuario($paramUsu);
        }
    }
}

its done
I just do it like this.

$param['clave'] = sha1($this->input->post('txtClave'));

You can use sha1 () as shown below:

$param['clave'] = sha1($this->input->post('txtClave'));