Sample Final Exam Questions

415.725SC Software Security

 

Clark Thomborson

Computer Science Department, University of Auckland

18 September, 2000

 

Instructions:  This exam will not be graded.  Write your answers on a separate sheet.  Do not write your name on your answer sheet.  If you turn in an answer sheet to me at the end of this class period, I may use one or more of your answers in a class discussion.

A.  Legal, Ethical and Conceptual Frameworks

1)      Consider the three goals of security, defined in Pfleeger’s book: confidentiality, integrity, availability.  Also consider his classification of assets: hardware, software, data.

Which of Pfleeger’s security goals, for which of Pfleeger’s asset classes, are protected by the following clause of the Computer Science Department’s Computer Systems Regulations of 17 September 1999:

“No person shall … use a login name other than the one(s) assigned to that person by the Department or allow any other person to use that person’s login name(s) to access one of the Department’s computer systems without the express permission of the Director of that system.”

Explain your answer briefly (in approximately 50 words).

B.  Cryptographic Authentication, e-Commerce, and Secure Communication

2)      The first step in Aucsmith’s “Identity Verification Protocol” is F0 = ( HA == K1A[ K-1A[ HA ] ] ).  In this formula, the variables have the following definitions:

·        HA is a hash value computed over the code of module A,

·        K-1A is a private key of the Integrity Verification Kernel (IVK) embedded in module A,

·        K1A is a public key of the IVK embedded in module A,

·        F0 is a flag value indicating the success or failure of an operation, and

·        K-1A[ HA ] is the signature of module A under A’s private key.  This value was computed at compile-time and is stored in some secret fashion within module A.

Which of the following phrases best describes this step in Aucsmith’s IVP?

a)      A verifies self

b)      A challenges E

c)      F verifies self

d)      E responds to A

e)      E verifies A

f)        A checks response

3)      Briefly explain (in approximately 50 words) the individual calculations or function evaluations made during the first step in Aucsmith’s IVP.

C.  Protection of Hosts

4)      Briefly describe one assumption about computer system security, which is valid for non-mobile systems, but is violated for mobile code systems.

D.  Copy Detection

5)      Consider the following images.


Figure 1. Checkerboard.

Text Box: Copyright 2000 C Thomborson
Figure 2. Copyright Notice.

Sketch the image that would result if the Checkerboard (Figure 1) is watermarked with the Copyright Notice (Figure 2), using the least-significant bit embedding described in the paper by Johnson and Jojodia.

6)      Characterise the watermarked image you constructed in your answer to the previous question, in terms of its fidelity, robustness, and security.  Use the definitions of Matheson et al. for these terms.

E.  Copy Prevention

7)      Consider the following assertion: “Any secrets carried in Java bytecode written today, could be easily attacked tomorrow by a reverse engineer who has access to the decompiler described by Proebsting and Watterson.”  Make a brief argument for, or against, this assertion.