diff --git a/authjwt.php b/authjwt.php
index 5e38356..d65dc5a 100644
--- a/authjwt.php
+++ b/authjwt.php
@@ -6,12 +6,15 @@
 
 require_once ("domframework/jwt.php");
 
-/** User authentication against JSON Web Token */
+/** User authentication against JSON Web Token
+  * To use it, the $serverKey must be defined. It can be created by example,
+  * by using $serverKey = sha1 (microtime (true));
+  */
 class authjwt extends auth
 {
   /** The JSON Web Token Server key if used
     */
-  public $jwtServerKey = null;
+  public $serverKey = null;
 
   /** If the user is valid, return the email in details
     */
@@ -41,7 +44,7 @@ class authjwt extends auth
       throw new \Exception ("No Bearer Authentication available", 401);
     $token = substr ($_SERVER["HTTP_AUTHENTICATION"], 7);
     $jwt = new jwt ();
-    $payload = $jwt->decode ($token, $this->jwtServerKey);
+    $payload = $jwt->decode ($token, $this->serverKey);
     if (! key_exists ("email", $payload))
       return null;
     // The JWT was tested in authparams. End of process