Answer the following questions in no more than six lines each. (3 x12 = 36)

1. Explain how a Smurf attack works.

2. Can the public key parameters be n = 15 and b = 6 in RSA? Why? (Of course the numbers are small and this is a toy example).

3. If you see several TCP SYN segments sent to a web server, but no ACK segments in the three-way handshake, what do you suspect may be happening? Explain.

4. Consider the network shown below.

Clients from the outside can only connect to the web server and mail server in the DMZ. Most hosts from the inside can connect only to the web server and mail server in the DMZ. Only the host 136.142.117.1 can connect to any web server on the outside. Design rules for packets entering only interface p for stateful packet filter A for the above security policy. You can use a mix of standard and extended ACLs or you can write your rules as sentences. Include details and add explanations as necessary. (24)

5. Alice and Bob are communicating using a shift cipher with the capital letters in English, but with a twist. They use two keys instead of one, and the keys alternate. So the first letter would be encrypted using the key k₁ = 9, the second using the key k₂ = 14, the third with k₁, the fourth with k₂ and so on as needed. Their hope is that this will prevent frequency analysis by Oscar.

a. Do you think this approach is secure? Why? Explain using Kerckhoffs principle and the effort that it may take Oscar to use brute force. (15)

b. Decrypt the following ciphertext exchanged by Alice and Bob (show steps): JWAVXDYSA (25)

6. The decrypted message in Problem 3(b) corresponds to an article that was assigned for your reading. Summarize the main idea of that article in no more than 6 lines. (10)