Consider a new block cipher, DES2, that consists only of two rounds of the Feistel structure (com- pared to 16 rounds for the noemal use of DES). DES2 has the same block and key size as DES. For this question, you should consider the DES round function F as a black box that takes two inputs, a 32-bit data segment and a 48-bit round key, and produces a 32-bit output. Do not look inside the S-boxes for this problem Suppose you have a large number of plaintext-ciphertext pairs for DES2 under a single unknown key. Give an algorithm for recovering the 48-bit round key for round 1 and the 48-bit round key for round 2. Your algorithm should require fewer operations than an exhaustive search for the entire 56-bit DES key