A company wants to transmit data over the telephone, but they are concerned that their phones may be tapped. All of their data is transmitted as four-digits. They have asked you to write a program that will encrypt their data so that it may be transmitted more securely. Your program should read a four-digit integer and encrypt it as follows: 1. Replace each digit by (the sum of that digit and 3) modulus 10. Then 2. Swap the first digit with the third, and swap the second digit with the fourth. 3. Print the encrypted integer.

def encrypt_digit(digit):

   if type(digit) is int or float:

       digit = str(digit)

   hold = list()

   for x in digit:

       d = str((int(x) + 3)%10)

       hold.append(d)

   first = hold.pop(0)

   second = hold.pop(0)

   third = hold.pop(0)

   fourth = hold.pop()

   print(int("".join([third,fourth, first, second])))

encrypt_digit(7836)

Explanation:

The python function accepts a four-digit parameter which represents the data transmitted over the company's telephone network. The function encrypts the data by adding 3 to each digit and getting the modulus of division 10, then the digits are swapped and printed out encrypted and ready for transmission.