Answer the following questions related to network security a) [5 points] Please identify the primary security issues in computer networks and discuss or present proper tools to address the identified security problems. b) [5 points] Please encrypt "machinelearningabc" with the transposition cipher, using a 6-bit key generated from your student ID. For example, pick up the first six different numbers from your student ID: 20450334-> 204534. If there are no enough different number of bits in the ID, you can arbitrarily add random numbers in the end, 204000205-> 204513. c) [5 points] How to launch a man-in-the-middle attack? (Illustrate the attack by providing detail message information of key exchange.)