Question 2. Consider the following correspondence between the first 16 English letters and the four-bit binary numbers 0000, 0001, ., 1111. A hybrid cryptosystem named SP-16 encrypts a message that is composed of letters from the first 16 English letters as follows: (1) Each letter of the message is replaced by the corresponding four-bit binary number (e.g., the message "man" is replaced by 1100 0000 1101). (2) The binary representation of the message from (1) is encrypted using the stream cipher with a key k = (k,.k2.k3.k.) consisting of 4 bits and with the key stream generator =k, for i=1,2,3,4, and where e, (x)-x, z z,4=(q+2+1,)mod2 for i21, (3) The result from (2) is divided into blocks of 4 bits each and then encrypted using the permutation cipher with a key of length 4 that permutes the bits ofeach block