$(1$ point$)$ This question concerns block cipher modes. We will use a simple affine cipher, which can be expressed in $C$ as follows.

char cipher$($unsigned char block, char key$)$

$\{$

return $(key+11**block)\%256$;

$\}$

Note that the block size is $8$ bits, which is one byte $($and one ASCII character$).$ We will work with the fixed key $008.$

We now encrypt various plaintexts using modes for this cipher. In every case in which the mode requires an IV$,$ the IV will be $0$xAA. In the case of CTR mode, we

use a $($nonce $||$ counter$)$ arrangement in which the nonce is the left $5$ bits of $0$xAA and the counter is a $3$ bit counter that begins at $0.$ In all of the problems given

below, one character is one block. Each character of the plaintext should be regarded as its corresponding ASCII code.

a$)$ Encrypt the plaintext "cheery" using $CTR$ mode. Please enter your answer in hex. $($Please do enter an $0x,$ as this has been done.$)$

b$)$ Encrypt the plaintext "chirper" using ECB mode. Please enter your answer in hex.

c$)$ Encrypt the plaintext "chafes" using $CFB$ mode. Please enter your answer in hex.

d$)$ Encrypt the plaintext "charges" using $CBC$ mode. Please enter your answer in hex.

e$)$ Encrypt the plaintext "chuff" using OFB mode. Please enter your answer in hex.