Let k, n 4 and let E: {0,1} * {0,1} {0,1} be a blockcipher. Define F:...

 

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Let k, n 4 and let E: {0,1} * {0,1}" {0,1}" be a blockcipher. Define F: {0,1}k+n {0,1}" {0,1}" as follows, for K = {0,1}k and K2, M = {0,1}": Alg F(K1||K2, M) CE(K, MK2) Return C Let TE denote the time for a computation of E/E-1. All times are worst case. (a) [6 points] Is F ia blockcipher? Answer YES or NO and prove your answer correct. (b) [4 points] How much time is taken by a 3-query exhaustive key search attack on F? Your answer should be a function of TE, k, n. (c) [10 points] Present in pseudocode a 1-query adversary A that has advantage Adv (A) = 1 and running time O(TE + k + n). kr (d) [20 points] Present in pseudocode a 3-query adversary A3 that has advantage Adv (A3) = 1 and running time O(2k. (TE+k+n)). Let k, n 4 and let E: {0,1} * {0,1}" {0,1}" be a blockcipher. Define F: {0,1}k+n {0,1}" {0,1}" as follows, for K = {0,1}k and K2, M = {0,1}": Alg F(K1||K2, M) CE(K, MK2) Return C Let TE denote the time for a computation of E/E-1. All times are worst case. (a) [6 points] Is F ia blockcipher? Answer YES or NO and prove your answer correct. (b) [4 points] How much time is taken by a 3-query exhaustive key search attack on F? Your answer should be a function of TE, k, n. (c) [10 points] Present in pseudocode a 1-query adversary A that has advantage Adv (A) = 1 and running time O(TE + k + n). kr (d) [20 points] Present in pseudocode a 3-query adversary A3 that has advantage Adv (A3) = 1 and running time O(2k. (TE+k+n)).