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(a) Alice wants to communicate with Bob securely using cryptosystem that provides secrecy and authentication. Alice decided to use public-key cryptosystem. Criticize the decision of Alice and illustrates if public-key cryptosystem fulfill Alice security requirements. (b) One local area network vender provides a key distribution facility, as illustrated in the bellow figure. Comment and describe the scheme. 2 Key Distribution Center (KDC) 3 A 1 (1) IDA, E(Ka, Na) (2) IDA, E(Ka, Na), IDB, E(Kb, Nb) (3) E(Kb, [Ks, IDA, Nb]), E(Ka, [Ks, IDB, Na]) (4) E(Ka, (Ks, IDB, Na])