Write a program that implements a bit stream cipher. An elementary level bit stream

cipher is an encryption algorithm that encrypts $1$ byte of plain text at a time. This cipher

uses a given $4-$bit bit pattern as the key. The size of the encrypted message that we want

to be able to send has a maximum length of $200$ characters. The $4-$bit pattern must be

duplicated to an $8-$bit value for this to work. $($e$.$g$.,$ if we have the $4-$bit pattern $0110,$

then the $8-$bit key would be $01100110.)$

Here is an example:

If we have the ASCII value for the letter $$t$,$ then that equates to the hex value $0$x$74,$

which represents the binary value $01110100.$ If we bitwise XOR that value with a key,

say $01010101,$ then

$01110100->$t$$

$01010101->$ XOR with key encryption

$00100001->$ encrypted value $0$x$21$