$($e$)$ The Caesar Cipher can be implemented by two $$wheels$,$ where each wheel has the letters of

the alphabet written on it and the inner wheel can be rotated within the outer wheel. Explain

how to encrypt and decrypt with the Caesar Cipher using such an implementation. $[2$ marks$]$

$($f$)$ The Simple Substitution Cipher is a major improvement on the Caesar Cipher. In what

different ways is it an improvement? $[2$ marks$]$

$($g$)$ If a Simple Substitution Cipher is used $($with an unknown key$)$ and we intercept the ciphertext

OXAO, then which of the following four$-$letter words could be the plaintext: JOHN, SKID,

SPAS, LOOT, PLOP, or OSLO? $[2$ marks$]$

$($h$)$ If a Simple Substitution Cipher is used $($with an unknown key$)$ and we intercept the ciphertext

BRKKLK$,$ then what do we know about the plaintext? $[2$ marks$]$

$($i$)$ Suppose in the case of intercepting BRKKLK we also know the plaintext is the name of a

country. What is the plaintext? $[2$ marks$]$

$($j$)$ What important lesson does the BRKKLK example illustrate? $[2$ marks$]$