Computer Network Security

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:
Hexadecimal notation: 0 1 2 3 4 5 6 7 8 9 A B C D E F
Binary notation: 0000 0001 0010 0011 0100 0101 0110 0111
1000 1001 1010 1011 1100 1101 1110 1111
a. Derive K1, the first-round subkey.
b. Derive L0, R0.
c. Expand R0 to get E[R0], where E[ # ] is the expansion function of Table S.1.
d. Calculate A = E[R0] ? K1.
e. Group the 48-bit result of (d) into sets of 6 bits and evaluate the corresponding
S-box substitutions.
f. Concatenate the results of (e) to get a 32-bit result, B.

g. Apply the permutation to get P(B).
h. Calculate R1 = P(B) ? L0.
i. Write down the ciphertext.

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