Question: (10pt) Suppose that you know a MAC value X and the key K that was used to compute the MAC, but you do not

(10pt) Suppose that you know a MAC value X and the key K that was used to compute the MAC, but you do not know the original message. (a) (8pt) Show that you can construct a message M that also has its MAC equal to X. Note that we are assuming that you know the key K and the same key is used for both MAC computations.2 (b) (2pt) How much of the message M are you free to choose? 2Hints: can we construct CN-2 first?
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To address this problem we first need to clarify that constructing another message M M such that its MAC is the same as a known MAC X X generally depe... View full answer
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