Define a message authentication function AHMACK (Append Hash MAC ) via

for any message M P1Pall 1P Assume that ITHAsH is not weakly collision resistant, and suppose an attacker knows a message/AHMAC pair (Mi, AHMAC(M)). Show how she can find (without knowl- edge of K) a second message/AHMAC pair (M2, AHMACK(M2)), thereby defeating computation resistance Hint: Note that on input any L-bit message, the first L rounds of the computation of AHMACK(M) do not depend on K, just on M