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2. [5 pts] Let II denote the Vigenre cipher where the message space consists of all 3-character strings (over the English alphabet), and the key is generated by first choosing the period t uniformly from {1,2,3} and then letting the key be a uniform string of length t. (a) Define A as follows: A outputs mo = aab and m = abb. When given a ciphertext c, it outputs 0 if the first character of c is the same as the second character of c, and outputs 1 otherwise. Com- pute Pr[Privka, i = 1]. (b) Construct and analyze an adversary A' for which Pr[Privky. = 1] is greater than your answer from part (a). 2. [5 pts] Let II denote the Vigenre cipher where the message space consists of all 3-character strings (over the English alphabet), and the key is generated by first choosing the period t uniformly from {1,2,3} and then letting the key be a uniform string of length t. (a) Define A as follows: A outputs mo = aab and m = abb. When given a ciphertext c, it outputs 0 if the first character of c is the same as the second character of c, and outputs 1 otherwise. Com- pute Pr[Privka, i = 1]. (b) Construct and analyze an adversary A' for which Pr[Privky. = 1] is greater than your answer from part (a)