totp based seat lock for activa

Basically, we are making a project using Arduino Uno and Gsm sim900A module,gps and safety alarm 1)Instead of typing a fixed password we want to send the password(4 digit) as an OTP to our mobile app in which user is registered. 2)There will be a dialler keypad in which user will type the otp received from our app using Google authentication API or any otp 3)Now , when we receive the OTP we will type it on the keypad and when it is verified it will switch on a motor(Door). 4)It must be secure and unhackable. and you have to provide us the programming codes used in this project as we need this too.