alice and bob are arguing about which method of multiple encryption they should use. alice wants to choose keys k1 and k2 and triple encrypt a message m as c = ek1 (ek2 (ek1 (m))). bob wants to encrypt m as c = ek1 (ek1 (ek2 (ek2 (m)))). which method is more secure? describe in detail an attack on the weaker encryption method.