Prove that the following modications of basic CBC-MAC do not yield a secure MAC (even for xed-length messages): (a) Mac outputs all blocks t1,...,t`, rather than just t`. (Verication only checks whether t` is correct.)

hint: the attack has oracel access to the MAC (training phase) to get a message and tag pair, then needs to output/find another pair to pass Vrfy, or find a different message with the same tag as the one in training phase.