Making encrypted phone calls over exachange using raspberry pi3

I need you to write program for me. I would like this software to be developed for Raspberry pi3 using Python. This will make raspberry pi take input of number from keyboard and make a encrypted call using dial up modem. At the reciever end it will have a modem in auto answer mode and recieve the call over reciever raspberry pi. This way i can make encrypted call over landline without using my phone but raspberry pi.