I$$d like to ask an expert

a$)$Use a hypothetical block cipher with a block length of $4,$defined as Ek$($b$1,$b$2.$b$3.$b$4)=($b$2,$b$3,$b$1.$b$4$

b$)$Convert English plaintext into a bit string using the table provided $($A$=0000$to P$=1111).$Assume we have a language that uses $16$letters only. If we want a more realistic exercise, we can have block size of $5$bits that can represent $32$cases $($more than $26$letters$)$or even size of $8$bits that use the ASCII. Here we just use the size of $4$bit

$2.$Encryption Modes: Encrypt the plaintext 'FOO' using the following modes. Convert the final ciphertexts into letters. Show your work

a$)$ECB $($Electronic Codebook$)$

b$)$CBC $($Cipher Block Chaining$)$with IV$=1010$

c$)$CTR $($Counter$)$with ctr$=1010$

$3.$Decryption Task:

Assume the ciphertexts from $2$are received by an intended receiver.

d$)$Manually decrypt each ciphertext to recover the original plaintext. Show your work