Your program should contain two parts: 1. depend on DES then Implement S1-box using C or C++. In your program, the input can be a bit string of length 6 or an integer between 0 and 63 (each of them can be converted into a bit string of length 6). The output should be an integer between 0 and 15 (which can be converted into a 4-bit string).

2. Write a procedure that takes as inputs a 6-bit string X and a 4-bit string Y , and outputs all 6-bit strings Z such that S1(Z) S1(Z X) = Y.

Notes: In C/C++, the operation is . Your program should be compilable with gcc or g++. Source code should be very well commented. Submit your C/C++ program and a readme.txt (instructions on how to compile and run your program) to the e-learning. date.