A free program for Android, by BinCorentin.

We have made a new and unique application that will allow you to set a passcode or a PIN to protect your privacy. It has amazing and modern wallpapers, fonts, date and time format, unlock text, etc. It will allow you to set a passcode to protect your privacy, or you can just use a slide to unlock without a pin code.

This app comes with cool street racing photos you can use as your lock screen. So you do not only have a protected phone, but also a stylish one. 

Don’t worry as this app does not consume your battery and memory storage much.