Hello, I am a student of Master’s Degree in Embedded Computing Systems offered by Sant’Anna School of Advanced Studies and the University of Pisa. I am carrying out a cyber security thesis project focusing in particular on Pointer Authentication of ARM. I have some questions: 1) why do you need XPAC * instruction? Is not it a problem for security in case of an attack? If so, is it possible to trap only the use of this instruction for a certain exception level? 2) When an authentication fails, a translation faults occurs. Is it possible to know, from the values of registers, that this is given by a failed authentication and not for another reason? 3) What types of attacks PAC can block and which ones do not? 4) Which ARM processors implement PAC?