If you want to keep the photos and files in your phone secret then use this application. This app will put a lock on your photos so that no one can access them. All you have to do is supply a password and click Lock button. After setting the password, whatever image you select, it will get locked. You can unlock the images by using this app only.
The best way to hide pictures out there. Gallery Vault can be hidden and this app will be required to unhide. Remember to unlock all your locked images before you decide to uninstall this application.