Q19) For 3DES, why not do a "double-encrypt" as C=E(E(P,K1),K2) ? That is, first encrypt P with K1 to get C1 =E(P,K1), then encrypt C1 using K2 to get C. Outline an attack to the above "double-encrypt" scheme. (Hint: Prof. Mark Stamp's lecture notes explained this. Understand it, and explain in your own words. Directly copying will result in 0 on this question and count as cheating!)