Due 11:10AM Wednesday, October 29, 2014. Submit your answers via Moodle in PDF form.
This is an open-notes, open-Internet, open-book exam. The only thing you aren't allowed to do is consult with other people about the exam (except for Jeff Ondich, with whom you may discuss the exam as much as you like).
Make your answers detailed, but also as clear and concise as possible. In this test, "detailed" usually means something like "give me a step-by-step description of who sends what to whom."
Cite your sources.
Because we're such rebels, we're going to do a gender-swap on this exam by replacing Alice, Bob, and Eve with Charlie, Donna, and Evander. Charlie initiates and Donna replies, while in the darkness, Evander pursues his evil plans.
(6 points) I encrypted a message for you using 256-bit AES in CBC mode, converting the resulting encrypted message into base64 so I could print it here.
(6 points) MACs
(10 points) Last Friday, we talked about Diffie Hellman for a minute. We noted that the pure DH protocol is vulnerable to a man-in-the-middle attack. But we also recalled that SSH uses DH to exchange essential secrets. This exercise is intended to explore whether SSH is simply vulnerable to MITM as a result, or whether there is protection built in, and if so, what is the nature of the protection.
(8 points) Being Evander: ARP Poisoning/Spoofing
(3 points) Identify two security incidents that you would be interested in studying to understand their technical details. When I hand back the exam, I'll let you know whether your ideas are suitable for the upcoming "explain a famous security breach" project. For this question only, you may consult with other students, including potential partners for the project.
(10 points) Charlie has a website. On this site, he has a page that includes his 2048-bit RSA public key, plus the following statement: "Whenever I email you an important attachment like a signed contract or a legal notice, I will also include a signature file consisting of the SHA-256 hash of the important document, encrypted using my public private [but see email from 10/28] key." Charlie goes on to explain how to check this signature against the document on various common platforms.
Your job is to list as many ways as you can think of for somebody to undermine Charlie's system. For each attack you come up with, briefly describe the practical barriers the attacker will face. (For example, if the attack is "compute Charlie's private key," you will want to observe that at present, there is no publicly published way to do that within the expected lifetime of anyone currently alive. So the practical barrier in this case is that the attacker will need to make a dramatic mathematical breakthrough.)