CSC 8222 Network Security
Homework 1
Name: _____________________________
* All the calculated answers must show the calculation procedure.
* Submit printed (e.g., no hand-writing) hard copy before the class on the due date.
1. (10 points) What are the four aspects of network security? What network security
mechanisms are designed to achieve them respectively?
2. (10 points) What are the two types of symmetric cryptography cipers? May you also
name at least one symmetric cryptography protocol for each type?
3.
(10 points) Using RSA, choose p=3 and q=11, and encode the word “hello”. Apply the
decryption algorithm to the encrypted version to recover the original plaintext message.
4. (10 points) In the man-in-the-middle attack in Figure 8.21 (or lecture slide 38 of
Overview.ppt), Alice has not authenticated Bob. If Alice want to require Bob to
authenticate himself using ap5.0, would the man-in-the-middle attack be avoided?
Explain your reasoning.
CSC 8222 Network Security
5.
(10 points) Suppose Alice wants to communicate with Bob using symmetric key
cryptography using a session key KS. In the lecture we learned how public-key
cryptography can be used to distribute the session key from Alice to Bob. In this
problem, we explore how the session key can be distributed—without public key
cryptography using a key distribution center (KDC). The KDC is a server that shares a
unique secret symmetric key with each registered user. For Alice and Bob, denote these
keys by KA_KDC and KB_KDC. Design a scheme that uses the KDC to distribute KS to Alice
and Bob. Your scheme should use three messages to distribute the session key: a message
from Alice to the KDC; a message from the KDC to Alice; and finally a message from
Alice to Bob.
6. (10 points) Alice sends a secure email to Bob with the mechanism in the following
diagram. Please illustrate how Bob can decode the message, verify that it is truly from
Alice. In other words, please draw the right side of the diagram.
CSC 8222 Network Security
7. (10 points) Describe a security hole in 802.11 WEP protocol.