You have to implement encryption and decryption with Simplified DES, as discussed in the class and in Stallings 3rd edition. The permutations IP, P10, P8, and SW, and the functions fk, F , and the S-box S0 are all as described, and can be hardwired into your program. For parts (a) and (b), you will use the original S1 box as described in Stallings 3rd edition. However, for part (c), you have to use a modified S-box S1. In the modified S1, the rows 0 and 2 are the same as described for the original S1, but the rows 1 and 3 have been switched. So row 1 is 2, 1, 0, 3 and row 3 is 2, 0, 1, 3. Your program should: take as input a 8-bit block of plaintext and a 10-bit key. Show the following output (please only print what is being asked for, and nothing else): (a) the intermediate result after the SW operation while encypting. (b) the ciphertext. (c) the intermediate result after the SW operation while decrypting. (d) the result of the decryption process. You have to run your programs on the following inputs: (a) with the original S1: the example from the textbook i.e. the plaintext is 10111101 and the key is 1010000010. In this case we know the ciphertext should come out to be 01110101, so this is a good way to check that your program is performing correctly on this input. (b) with the original S1: the plaintext is 11010111 and the key is 1111100110. (c) with the modified S1: the plaintext is 11100101 and the key is 0100110101. Please note that you do not have to actually implement these operations as bit operations. For example, you can store the plaintext as an array of integers. If you find it easier, you can hard-wire the S-boxes (S0,S1,S1) in your program. Extra Credit Programming Problem 1: Implement (program) an attack on the Hill cipher as discussed in class and the textbook. Your attack should work on a 2 2 matrix. Show how your attack works on the example on page 84, and also run it on some other inputs. Extra Credit Programming Problem 2: Implement (program) a brute-force attack on Simplified Des. Show how your attack works on an example.

Python is preferred.