diff --git a/application/config/constants.php b/application/config/constants.php
index 76631502c..5e0c9e66e 100644
--- a/application/config/constants.php
+++ b/application/config/constants.php
@@ -20,6 +20,52 @@ define('FHC_NORIGHT', 5); 	    // No rights
 define('FHC_INVALIDID', 6); 	// Invalid or no ID (key)
 define('FHC_NOPK', 7); 			// No primary key
 
+/*
+|--------------------------------------------------------------------------
+| Exit status codes
+|--------------------------------------------------------------------------
+|
+| Used to indicate the conditions under which the script is exit()ing.
+| While there is no universal standard for error codes, there are some
+| broad conventions.  Three such conventions are mentioned below, for
+| those who wish to make use of them.  The CodeIgniter defaults were
+| chosen for the least overlap with these conventions, while still
+| leaving room for others to be defined in future versions and user
+| applications.
+|
+*/
+define('EXIT_SUCCESS', 0); // no errors
+define('EXIT_ERROR', 1); // generic error
+define('EXIT_MODEL', 2); // model error
+define('EXIT_CONFIG', 3); // configuration error
+define('EXIT_UNKNOWN_FILE', 4); // file not found
+define('EXIT_UNKNOWN_CLASS', 5); // unknown class
+define('EXIT_UNKNOWN_METHOD', 6); // unknown class member
+define('EXIT_USER_INPUT', 7); // invalid user input
+define('EXIT_DATABASE', 8); // database error
+define('EXIT_VALIDATION_UDF',				10); // UDF validation has been failed
+define('EXIT_VALIDATION_UDF_MIN_VALUE',		11); // UDF validation has been failed -> MIN VALUE
+define('EXIT_VALIDATION_UDF_MAX_VALUE',		12); // UDF validation has been failed -> MAX VALUE
+define('EXIT_VALIDATION_UDF_MIN_LENGTH',	13); // UDF validation has been failed -> MIN LENGTH
+define('EXIT_VALIDATION_UDF_MAX_LENGTH',	14); // UDF validation has been failed -> MAX LENGTH
+define('EXIT_VALIDATION_UDF_REGEX',			15); // UDF validation has been failed -> REGEX
+define('EXIT_VALIDATION_UDF_REQUIRED',		16); // UDF validation has been failed -> REQUIRED
+define('EXIT_VALIDATION_UDF_NOT_VALID_VAL',	17); // UDF validation has been failed -> Not valid value, object or array
+
+define('EXIT_AUTO_MIN', 1000); // lowest automatically-assigned error code
+define('EXIT_AUTO_MAX', 2000); // highest automatically-assigned error code
+
+/*
+|--------------------------------------------------------------------------
+| Authentication constants
+|--------------------------------------------------------------------------
+*/
+// Authentication methods
+define('AUTH_SESSION', 'session');
+define('AUTH_LDAP', 'ldap');
+define('AUTH_DB', 'database');
+define('AUTH_SSO', 'sso');
+
 /*
 |--------------------------------------------------------------------------
 | File and directory modes
@@ -67,41 +113,6 @@ define('FOPEN_READ_WRITE_CREATE_STRICT', 'x+b');
 */
 define('SHOW_DEBUG_BACKTRACE', TRUE);
 
-/*
-|--------------------------------------------------------------------------
-| Exit status codes
-|--------------------------------------------------------------------------
-|
-| Used to indicate the conditions under which the script is exit()ing.
-| While there is no universal standard for error codes, there are some
-| broad conventions.  Three such conventions are mentioned below, for
-| those who wish to make use of them.  The CodeIgniter defaults were
-| chosen for the least overlap with these conventions, while still
-| leaving room for others to be defined in future versions and user
-| applications.
-|
-*/
-define('EXIT_SUCCESS', 0); // no errors
-define('EXIT_ERROR', 1); // generic error
-define('EXIT_MODEL', 2); // model error
-define('EXIT_CONFIG', 3); // configuration error
-define('EXIT_UNKNOWN_FILE', 4); // file not found
-define('EXIT_UNKNOWN_CLASS', 5); // unknown class
-define('EXIT_UNKNOWN_METHOD', 6); // unknown class member
-define('EXIT_USER_INPUT', 7); // invalid user input
-define('EXIT_DATABASE', 8); // database error
-define('EXIT_VALIDATION_UDF',				10); // UDF validation has been failed
-define('EXIT_VALIDATION_UDF_MIN_VALUE',		11); // UDF validation has been failed -> MIN VALUE
-define('EXIT_VALIDATION_UDF_MAX_VALUE',		12); // UDF validation has been failed -> MAX VALUE
-define('EXIT_VALIDATION_UDF_MIN_LENGTH',	13); // UDF validation has been failed -> MIN LENGTH
-define('EXIT_VALIDATION_UDF_MAX_LENGTH',	14); // UDF validation has been failed -> MAX LENGTH
-define('EXIT_VALIDATION_UDF_REGEX',			15); // UDF validation has been failed -> REGEX
-define('EXIT_VALIDATION_UDF_REQUIRED',		16); // UDF validation has been failed -> REQUIRED
-define('EXIT_VALIDATION_UDF_NOT_VALID_VAL',	17); // UDF validation has been failed -> Not valid value, object or array
-
-define('EXIT_AUTO_MIN', 1000); // lowest automatically-assigned error code
-define('EXIT_AUTO_MAX', 2000); // highest automatically-assigned error code
-
 /*
 |--------------------------------------------------------------------------
 | Email constants
diff --git a/application/controllers/api/v1/CheckUserAuth.php b/application/controllers/api/v1/CheckUserAuth.php
index 181c68ca1..d9d6cb1a8 100644
--- a/application/controllers/api/v1/CheckUserAuth.php
+++ b/application/controllers/api/v1/CheckUserAuth.php
@@ -1,21 +1,7 @@
 <?php
-/**
- * FH-Complete
- *
- * @package		FHC-API
- * @author		FHC-Team
- * @copyright	Copyright (c) 2016, fhcomplete.org
- * @license		GPLv3
- * @link		http://fhcomplete.org
- * @since		Version 1.0
- * @filesource
- */
-// ------------------------------------------------------------------------
 
 if (!defined('BASEPATH')) exit('No direct script access allowed');
 
-require_once APPPATH.'/libraries/REST_Controller.php';
-
 class CheckUserAuth extends REST_Controller
 {
 	/**
@@ -24,6 +10,10 @@ class CheckUserAuth extends REST_Controller
 	public function __construct()
 	{
 		parent::__construct();
+
+		// Loads helper message to manage returning messages
+		// NOTE: loaded here because it does not extend the APIv1_Controller
+		$this->load->helper('hlp_message');
 	}
 
 	/**
@@ -36,7 +26,7 @@ class CheckUserAuth extends REST_Controller
 
 		if (isset($username) && isset($password))
 		{
-			$result = $this->authlib->CheckUserAuthByUsernamePassword($username, $password);
+			$result = $this->authlib->checkUserAuthByUsernamePassword($username, $password);
 
 			$this->response($result, REST_Controller::HTTP_OK);
 		}
@@ -63,18 +53,18 @@ class CheckUserAuth extends REST_Controller
 		// If username and password are given then check authentication using them
 		if (isset($username) && isset($password))
 		{
-			$result = $this->authlib->CheckUserAuthByUsernamePassword($username, $password, true);
+			$result = $this->authlib->checkUserAuthByUsernamePassword($username, $password, true);
 		}
 		elseif (isset($code) || isset($email))
 		{
 			// If code and email are given then check authentication using them
 			if (isset($code) && isset($email))
 			{
-				$result = $this->authlib->CheckUserAuthByCodeEmail($code, $email);
+				$result = $this->authlib->checkUserAuthByCodeEmail($code, $email);
 			}
 			else // otherwise check authentication using only code
 			{
-				$result = $this->authlib->CheckUserAuthByCode($code);
+				$result = $this->authlib->checkUserAuthByCode($code);
 			}
 		}
 
diff --git a/application/core/APIv1_Controller.php b/application/core/APIv1_Controller.php
index b2cd98051..1efbe5600 100644
--- a/application/core/APIv1_Controller.php
+++ b/application/core/APIv1_Controller.php
@@ -1,7 +1,5 @@
 <?php
 
-require_once APPPATH.'/libraries/REST_Controller.php';
-
 class APIv1_Controller extends REST_Controller
 {
 	/**
diff --git a/application/libraries/REST_Controller.php b/application/core/REST_Controller.php
similarity index 99%
rename from application/libraries/REST_Controller.php
rename to application/core/REST_Controller.php
index 7575862ba..0e4ef7266 100644
--- a/application/libraries/REST_Controller.php
+++ b/application/core/REST_Controller.php
@@ -1799,8 +1799,8 @@ abstract class REST_Controller extends CI_Controller {
             return FALSE;
         }
 
-        $auth_library_class = strtolower($this->config->item('auth_library_class'));
-        $auth_library_function = strtolower($this->config->item('auth_library_function'));
+        $auth_library_class = $this->config->item('auth_library_class');
+        $auth_library_function = $this->config->item('auth_library_function');
 
         if (empty($auth_library_class))
         {
@@ -1814,15 +1814,12 @@ abstract class REST_Controller extends CI_Controller {
             return FALSE;
         }
 
-		// Loads authentication library
-		$this->load->library('AuthLib');
-
         if (is_callable([$auth_library_class, $auth_library_function]) === FALSE)
         {
-            $this->load->library($auth_library_class);
+            $this->load->library($auth_library_class, array(false));
         }
 
-        return $this->{$auth_library_class}->$auth_library_function($username, $password);
+        return $this->{strtolower($auth_library_class)}->$auth_library_function($username, $password);
     }
 
     /**
diff --git a/application/helpers/hlp_authentication_helper.php b/application/helpers/hlp_authentication_helper.php
index dd25b2a38..abf85a7a3 100644
--- a/application/helpers/hlp_authentication_helper.php
+++ b/application/helpers/hlp_authentication_helper.php
@@ -1,61 +1,22 @@
 <?php
 
-/**
- * FH-Complete
- *
- * @package	FHC-Helper
- * @author	FHC-Team
- * @copyright	Copyright (c) 2016 fhcomplete.org
- * @license	GPLv3
- * @link	https://fhcomplete.org
- * @since	Version 1.0.0
- * @filesource
- */
-
-if (! defined('BASEPATH')) exit('No direct script access allowed');
-
-require_once FHCPATH.'include/authentication.class.php';
+if (!defined('BASEPATH')) exit('No direct script access allowed');
 
 // ------------------------------------------------------------------------
 // Functions needed to manage the user authentication
 // ------------------------------------------------------------------------
 
-if ( ! function_exists('auth'))
-{
-	/**
-	 * Auth Username, Password over FH-Complete
-	 *
-	 * @param	string	$username
-	 * @param	string	$password
-	 * @return	bool
-	 */
-	function auth($username, $password)
-	{
-		$auth = new authentication();
-		if ($auth->checkpassword($username, $password))
-		{
-			echo 'Auth-Method-False';
-			return true;
-		}
-		else
-		{
-			echo 'Auth-Method-False';
-			return false;
-		}
-	}
-}
-
 /**
- * Look if User is logged in and return uid
- * it tries to work always with CI session
- * Otherwise return false
+ * It calls the AuthLib, if the user is NOT logged then the login page is shown
+ * If the user is alredy logged, then it is possible to access to the authentication object
+ * that contains the username of the logged user
  *
- * @return	string or (bool)false
-*/
+ * @return string or null
+ */
 function getAuthUID()
 {
 	$ci =& get_instance(); // get CI instance
 	$ci->load->library('AuthLib'); // load authentication library
 
-	return $ci->authlib->getUser();
+	return ($ci->authlib->getAuthObj())->{AuthLib::AO_USERNAME};
 }
diff --git a/application/libraries/PermissionLib.php b/application/libraries/PermissionLib.php
index 980598d9b..ae68837f8 100644
--- a/application/libraries/PermissionLib.php
+++ b/application/libraries/PermissionLib.php
@@ -65,7 +65,7 @@ class PermissionLib
 		{
 			// API Caller rights initialization
 			self::$bb = new benutzerberechtigung();
-			self::$bb->getBerechtigungen($this->_ci->authlib->getUser());
+			self::$bb->getBerechtigungen(($this->_ci->authlib->getAuthObj())->{AuthLib::AO_USERNAME});
 		}
 	}