We worked on the DESX, which we created by adding an XOR in front of and behind the DES. Let's cancel the first of these XORs (the one before DES). So, y = DES_k (x) XOR k1 (y ciphertext, x publictext, k and k1 secret keys) a) Write the decryption function. b) Can a meet-in-the-middle attack be applied to this cipher? If applicable, how? If not, why? Explain.