Question: Let F be a pseudorandom function. Show that the following MAC for messages of length 2n is insecure: Gen outputs a uniform k {0, 1}

Let F be a pseudorandom function. Show that the following MAC for messages of length 2n is insecure: Gen outputs a uniform k {0, 1} n. To authenticate a message m1km2 with |m1| = |m2| = n, compute the tag Fk(m1) k Fk(Fk(m2)).

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