Homework 1

Due back: April 27, 11:59pm, 2008 (by submission timestamp).

Submission: Electronic submission to ychen@northwestern.edu

Notes: 1. To be done by each group.

2. Please do not give a simple yes/no as results to some of the questions. Briefly explain why and how you obtain that result.

1. KPS problem 9-2

2. KPS problem 11-5

3. Consider the KDC and CA servers. Suppose a KDC goes down. What is the impact on the ability of parties to communicate securely; that is, who can and cannot communicate? Justify your answer. Suppose now a CA goes down. What is the impact of this failure?

4. Assume a client machine authenticates a user to a remote server over a clear text channel. The following table refers to three authentication methods. Write yes/no in the following table cells.

	Vulnerable to network sniffing	Vulnerable to dictionary attacks	Client can change his secret in case of a compromise
Plaintext passwords
Plaintext biometrics		N/A
Challenge response with user secret on smartcard			Yes