Assignment $(4)$

For this assignment, you'll work through the simplified version of the

DES algorithm $($S$-$DES$)$ we discussed in class. S$-$DES is not

cryptographically secure$,$ yet its operations are similar enough to the

inner workings DES, giving a better feel for how it works.

As mentioned in class, each block is $8$ bits, and the key is $10$ bits.

Perform just one round operation of the S$-$DES for the following

$8-$bit input.

Input $10011101$

Find the output which becomes the input for the next round

using the following figure.

For the key, convert the last $3$ digits of your student ID to

binary and use that value as the key. "For example, if your

Student ID is s$437021872,$ then you'd convert $872$ to

binary, which is $1101101000."$

Use the first letter of your name as the plaintext. "For

example, if your name is Ziad, then the first letter is $Z,$

which is $01011010$ in binary".

Now use S$-$DES to encrypt the first letter of your name

using the last $3$ digits in your student ID as the key. Show

all the steps of this encryption process.