This problem provides a numerical example of encryption using a one-round version of DES. We start with the same bit pattern for the key K and the plaintext, namely:

Binary notation: 1000 1001 1010 1011 1101 1100 1111 1110 0000 0001 0010 0011 0100 0101 0110 0111

a. Derive K1 , the first-round subkey.

(i). show the result after permutation 1.

(ii). Based on the result of a.(i)., show the result after leftshift.

(iii). Based on the result of a.(ii)., show the result after the permutation 2.

b. Derive L0, R0. (L0, R0 are obtained after initial permutation)

c. Expand R0 to get E[R0], where E[] is the expansion function.

d. Calculate A=E[R0]K1.

e. Group the 48-bit result of (d) into eight sets of 6 bits and conduct the substitutions with S-Box.

f. Lets use letter B to present the result obtain from step e. Apply the permutation function on B to get P(B).

g. Calculate R1=PBL0.

h. Do the 32 bit swap. (i.e. L1||R1 --> R1||L1)

i. Apply the inverse initial permutation on the results we got from h. That output is the ciphertext of one round version of DES.