Practical $1$:

The DES $($Data Encryption Standard$)$ algorithm is a symmetric$-$key block cipher created in the early $1970$s by an IBM team and adopted by the National Institute of Standards and Technology $($NIST$).$ The algorithm takes the plain text in $64-$bit blocks and converts them into ciphertext using $48-$bit keys. Simplified DES, developed by Professor Edward Schaefer of Santa Clara University, is an educational rather than a secure encryption algorithm

The S$-$DES encryption algorithm takes an $8-$bit block of plaintext $($example: $10111101)$ and a $10-$bit key as input and produces an $8-$bit block of ciphertext as output.

The S$-$DES decryption algorithm takes an $8-$bit block of ciphertext and the same $10-$bit key used to produce that ciphertext as input and produces the original $8-$bit block of plaintext.

The S$-$DES encryption algorithm takes an $8-$bit block of plaintext $($example: $10111101)$ and a $10-$bit key as input and produces an $8-$bit block of ciphertext as output. The S$-$DES decryption algorithm takes an $8$bit block of ciphertext and the same $10-$bit key used to produce that ciphertext as input and produces the original $8-$bit block of plaintext.

Consider the S$-$DES shown on the next page. The keys k $1$ and k$2$ can be derived using the functions P$10,$ Shift, and P$8.$ Given the below definitions of P$10$ and P$8,$ answer the questions that follow using $1010000010$ as the $10-$bit key.

$\backslash$table$[[,,,,],[3,,,,]]$

Compute the values of $k1$ and $k2$

Compute the first permutation $($IP$)$ of the following plaintext strings

a$.00111000.$

b$.10010010.$

OIT$216$ and $236$ Practical ONE

Figure $1$: Simplified DES