Recall that AIP enables a secure shut-off protocol to counter against Denial-of-Service (DoS) attacks, wherein the victim can send a shut-off message to the attacker to have him stop sending packets. The format of the shut-off message that a victim can send to the source is: Victims public key, Hash of packet received from the source, and TTL, which are all signed with Victims private key. Assume that AIP has been deployed worldwide in a way described in the lecture. In this scenario, are the following DoS attacks possible? Please also justify your answer.

(a) Consider an attacker M who is on the path of the connection between A and B, and wants to disrupt their communication. 1. M sends a shut-off message to B, by impersonating A, to prevent B from sending legitimate traffic to A. 2. M eavesdrops a packet from B to A, and then sends the same packet to A, by impersonating B, large enough number of times until A sends a shut-off message to B, then preventing B from sending legitimate traffic to A.

(b) Next, let us consider an attacker M who wants to launch a DoS attack against a server S. 1. M launches a DDoS by instructing a number of bots to send sufficient number of fake shut-off messages to S such that S is fully occupied for validating the large number of shut-off messages.

2. M creates a number of fake EIDs and launches a DoS on S using each of them. 3. M colludes with another attacker M such that they share a link between them which S uses to connect to the Internet. Both of them then congest that link, thus disconnecting S from the Internet.