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

class Login extends CI_Controller
{
	public function index()
	{
		if(!$this->session->userdata('loggedin'))
		{
			$this->load->view('login');
		}
		else
		{
			redirect('homepage');
		}
	}

	public function authentication()
	{
		$this->load->model('login_model', 'user');
		$username = $this->input->post('Username');
		$password = $this->input->post('Password');
		$sha_pass = sha1(strtoupper($password));
		$this->user->Auth($username, $sha_pass);
	}

	public function logout()
	{
		$this->load->model('login_model', 'user');
		$this->user->LogOut();
	}
}




################# MODEL ###########################
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Login_model extends CI_Model
{
	function __construct()
	{
		parent::__construct();
	}

	function Auth($username, $password)
	{
		if($this->DBAuth($username, $password))
		{
			$data = array(
			'username' => $username,
			'password' => $password,
			'loggedin' => TRUE
			);
			$this->session->set_userdata($data);
			redirect('homepage');
		}
		else
		{
			echo 'Invalid Password';
		}
	}

	function DBAuth($username, $password)
	{
		$sha_pass = sha1(strtoupper($password));
		$query = $this->db->select('username, password')->from('users')->where('username', $username)->where('password', $sha_pass)->get();
		if($query->num_rows() > 0)
			return true;
		else
			return false;
	}

	function LogOut()
	{
		$this->session->sess_destroy();
		redirect('login');
	}
}