University of Kansas

Electrical Engineering & Computer Science

EECS 563 - Homework Assignment

Homework - 12

1)      A department of 10 people needs to communicate securely, if they use a symmetric key system how many keys are needed? As the number of people increases what are some problems with distribution of symmetric keys. How are symmetric keys distributed?

2)      In public key systems all keys are publically available. True or False.

3)      In the digital signature technique, the sender uses which of the following keys create the cipher text:

a)      The senders own symmetric key

b)      The senders own private key

c)      The senders own public key

d)      The receiver’s private key.

4) What is the role of the hash fuction in digital signature?

5)      What is trusted third party in symmetric key systems.

6)     What certifies the binding between a public key and its owner?

a)      CA

b)      KDC

c)      Hash

d)      Digital signature

7)      In IPSec what is the difference between transport and tunnel modes?

8) Suppose a directory that stores certificates is broken into and the certificates in the directory are replaced by bogus certificates (but the CA's private key is not disclosed)? Explain why users will still be able to identify these certificates as bogus.

9) View a certificate used by your browser. In Firefox, go to Tools-->Options-->Advanced-->Encryption-->View Certificates-->Servers-->double click on any Certificate in the list. (For IE go to for instructions.)

a) Certificate Name

b) Who issued the certificate?

c) Who was the certificate issued to?

d) When does the certificate expire? Why do certificates expire?

10) Read Trying to Keep Your E-Mails Secret When the C.I.A. Chief Couldn't by NICOLE PERLROTH November 16, 2012, New York Time.

a) What was the role of hotel WiFi networks in finding Ms. Broadwell's computer?

b) What is Wickr?

c) What is Tor?


Victor S. Frost, and some problems from Main Text: Communication Networks: Fundamentals Concepts and
Key Architectures, A. Leon-Garcia and I. Widjaja (Second edition)