Recall that for a block cipher, a key schedule algorithm determines the subkey for each round, based on the key K. Let K = (fcofci&2 · · · ^55) be a 56-bit DES key. a. List the 48 bits for each of the...

Recall that for a block cipher, a key schedule algorithm determines the subkey for each round, based on the key K. Let K = (fcofci&2 · · · ^55) be a 56-bit DES key.

a. List the 48 bits for each of the 16 DES subkeys K\, K_i, ■ ■ ■, Kie, in terms of the key bits fcj.

b. Make a table that contains the number of subkeys in which each key bit k_i
is used.

c. Can you design a DES key schedule algorithm in which each key bit is used an equal number of times?