Need to add Password for my DTMF based Land rover

In my project one cell phone is attached to rover and one is with user.
When the user calls the cellphone attached to the rove, cell phone on r auto answers the call. And then when user press key 2 it moves forward and when pressed 8 it moves backward and also it has many moves.

But the problem is i want to add password. I want to add password such a that when the call is received then user have to press specific password and then when he/she press two 2 the rover moved forward. If after receiving the call user don’t enter the 4 digit password and he presses key 2 the rover should not move forward. ( also i have added ultrasonic obstacles detection but ignore that part )

Please help me how can i add this thing. My code is given below

Please post the code in line, using code tags, as described in How to use this forum.

To put your code in a code box, use the </> icon in the far left of the post tool bar and paste your code between the two bracket sets that appear.

To go back and put your code in a code box, in the bottom right of your post, select “more” and click modify. When the modify post opens, high light your code and click the </> in the far left of the post tool bar. This will put you code in code brackets. Then save the changes.