Using S-des to write a matlab code or C++ for question 3.18 .

without knowledge of the secret key k. (A"c has the ability to choose a ciphertext and then obtain its decryption. Here, you have 128 plaintext/ciphertext pairs to work with and you have the ability to chose the value of the ciphertexts) en iphertext" means that an adversary Note: The following problems refer to simplifed DES, described in Appendix G 3.16 Refer to Figure G.2, which depicts key generation for S-DES 3.17 The equations for the variables q and r for S.DES are defined in the section on 3.18 Using S-DES, decrypt the string (10100010) using the key (0111111101) by hand. a. How important is the initial P10 permutation function? b. How important are the two LS-1 shift functions? S-DES analysis. Provide the equations for s and t Show intermediate results after each function (IP, Fx SW, FK.IP).Then decode the first 4 bits of the plaintext string to a letter and the second 4 bits to another letter where we encode A through P in base 2 (ie.. A(xxx). I. 0001,-.-. P-11 ii ). Hint: As a mid- way check, after the application of SW, the string should be (00010011). Programming Problems 3.19 Create software that can encrypt and decrypt using a general substitution block cipher 3.20 Create software that can encrypt and decrypt using S-DES Test data: use plaintext ciphertext, and key of Problem 3.18