Suppose that a particular cipher uses a 40-bit key, and the cipher is secure (i.e., there is no known shortcut attack). a. How much work, on average, is an exhaustive search attack? b. Outline an...

Suppose that a particular cipher uses a 40-bit key, and the cipher is secure (i.e., there is no known shortcut attack).

a. How much work, on average, is an exhaustive search attack?

b. Outline an attack, assuming that known plaintext is available.

c. How would you attack this cipher in the ciphertext-only case?