Chapter 21, Problem 21.7E

(Simple Encryption) Some information on the Internet may he encrypted with a simple algorithm known as “rot 13,” which rotates each character by 13 positions in the alphabet. Thus. ' a’ corresponds to ‘n’, and 'x' corresponds to 'k'. rot 13 is an example of symmetric key encryption, with symmetric key encryption, both the encrypter and decrypter use the same key.

1. Write a program that encrypts a message using rot 13.
2. Write a program that decrypts the scrambled message using 13 as the key.
3. After writing the programs of part (a) and part (b), briefly answer the following question: If you did not know the key for part (b), how difficult do you think it would be to break the code? What if you had access to substantial computing power (e.g., supercomputers)? In Exercise 21.24 we ask you to write a program to accomplish this.