/**
  * @param string $sharedKey set and verify the shared key (if invalid, log a warning)
  */
 public static function setSharedKey($sharedKey)
 {
     if ($sharedKey != null) {
         if (strlen($sharedKey) < 10) {
             error_log("i>clicker shared key ({$sharedKey}) is too short, must be at least 10 chars long. SSO shared key will be ignored until a longer key is entered.");
         } else {
             self::$block_iclicker_sso_enabled = true;
             self::$block_iclicker_sso_shared_key = $sharedKey;
             if (!self::$test_mode) {
                 error_log("i>clicker plugin SSO handling enabled by shared key, note that this will disable normal username/password handling");
             }
         }
     }
 }