Data encryption standard $($DES$)$ is a well$-$known block$-$cipher in modern information security, and triple DES $(3$DES$)$ is an improvement of DES, creating better security. Simplified DES $($S$-$DES$)$ is a simplified version of DES, used mostly for educational purposes.

For this question, you are required to study the technical differences between DES, $3$DES and S$-$DES. Write a summary of the differences you find and then, using S$-$DES, decrypt by hand the string $(10100010)$ using the key $(0111111101).$ Show the intermediate results after each function $($IP$,$ FK$,$ SW$,$ FK$,$ IP$1).$ Then, decode the first four bits of the plaintext string to a letter and the second four bits to another letter, where we encode A through P in base $2($i$.$e$.,$ A $=0000,$ B $=0001,...,$ P $=1111).$