Homework

Part 1: Determine if the following statements are True or False and you must defend your answer in a short paragraph and cite all sources of information if any. Each question is worth 3 points.

1. T F Consider data that is stored over time in a mandatory access control based system. The contents of files containing highly classified (“top secret”) information are necessarily more trustworthy than material stored in files marked unclassified.

2. T F With unlimited resources and security controls, it is possible to reduce risk to zero.

3. T F The purpose of the DSS algorithm is to enable two users to securely reach agreement about a shared secret that can be used as a secret key for subsequent symmetric encryption of messages.

4. T F Viruses infect executable files and hardware as well.

Part 2: Short Answers (10 points each). Please answer briefly and completely, and you must cite all sources of information.

1. Assume that passwords are limited to the use of the 95 printable ASCII characters and that all passwords are 12 characters in length. Assume a password cracker with an encryption rate of 8 giga encryptions per second. How many years will it take to test exhaustively all possible passwords on a UNIX system? Note: You must show the procedures of calculation as well.

2. Consider a public key encryption. Ann wants to send Bill a message. Let Ann_priv and Ann_pub be Ann’s private and public keys respectively. The same for Bill (Bill_priv and Bill_pub).

(a) If Ann sends a message to Bill, what encryption should Ann use so that only Bill can decrypt the message (secrecy)? (3 points)

(b) Can Ann encrypt the message so that anyone who receives the message is assured that the message only came from Ann (authenticity)? (3 points)

(c) Is it possible for Ann to devise a method that will allow for both secrecy and authenticity for her message? Please justify your answer. (4 points)