Question 3 (5 points) Suppose a Certificate Authority (CA) with a well-known public key has issued a certificate to every user for his/her public key. For convenience, we use KAU and KAR to represent user A's public key and private key, respectively. Suppose Alice wants to send a large secret message M to Bob in an efficient way. Draw a diagram to describe (1) how Alice should send M in an authenticated way to Bob and (2) how Bob should process the received message sent by Alice. Question 4 (5 points) Suppose we place a filtering firewall between a LAN and the Internet as shown in Figure 1 below, where the labels on the arrows indicate the physical ports on the firewall router. The LAN hosts inside the firewall have IP addresses described by the regular expression 200.150.22.*. Figure 1. Firewall to protect the LAN. The filter table for port i2 is: The filter tables for ports o1 and o2 permit all traffic. 1. For each of the following packet descriptions arriving at port i2 of the firewall, fill in which line of i2 's filter table will be used to determine whether the packet is Rejected or Accepted. Each answer should be a single number 1, 2,3, or 4 . 2. Suppose that you want the policy on out-bound connections from the LAN to be as liberal as possible while still preventing IP spoofing from with the LAN. Complete the filter table for port i1