CS 160 Outlab

October 15, 2007

To Do:

The country of Hunteroen has critical data it needs to send to it's spies around the world. Hunteroen does not want the data to be intercepted and the knowledge stolen. The country of Hunteroen has hired you to write a program that will encrypt the data so that it may be transmitted more securely, and then the program will also have to decrypt the data again so you can have original data back.
All the data being transmitted are 4-digit integers. Your application should read a four digit integer entered by the user and encrypt it as follows:

Replace each digit with the result of adding 7 to the digit and getting the remainder after dividing the new value by 10.
Then swap the first digit with the third digit, and the second digit with the fourth.
Print the encrypted integer.
Next Write a method that takes the ecrypted four-digit integer and decrypts it to form the original number.
Do not use Strings or convert the integer to a String, keep them as integers.

You will need to add the following items:

The program should keep running and letting you encrypt numbers until a zero is given by the user
When the user enters a zero your program should print out goodbye, no other output, and exit.
When the user gives any other number(you can assume it's going to be 4 digits) your program should call one method for encrypting the number, and then call another method with the encrypted number and decrypt it. Don't just print out the first number, go through the steps and write a decryption algorithm.
Do not use Strings, use integers, and the input should be a 4 digit integer. Don't give 4 seperate ints between 0-9. Take a number like 3487, that's three thousand four hundred and eighty seven.
For every rule you break you will get points taken off.
Use division, remainders and math to seperate each of the four digits by its place in the number.

Here is sample output of the program executing:

  Please give a 4 digit integer (zero to quit):
9876
The encrypted number: 4365
The decrypted number: 9876

Please give a 4 digit integer (zero to quit):
3697
The encrypted number: 6403
The decrypted number: 3697

Please give a 4 digit integer (zero to quit):
1234
The encrypted number: 189
The decrypted number: 1234

Please give a 4 digit integer (zero to quit):
0
Goodbye

Turn in

This program is due at the beginning of your next lab class (October 23rd).

Hint

When you have a number like 5893 you can break down the digits by using mod and division, then subtraction to get a new number for the next digit.