Take Home Final Exam

CSE 227 Winter 2003

The answers to this final exam are due midnight, Friday Mar 21st,
2003.  You should email the answers to me at
bsy+cse227.w03@cs.ucsd.edu.  Make sure that your email works!  You can
cc to yourself, and on Unix systems use the mailq command to see if
the mail is actually getting delivered.

1. In cryptography, protocol designers assume that the cryptographic
   algorithm and protocol are known to the attacker, and the security
   analysis attempts to bound the success probability of the attacker
   as a function of expended effort, with no other assumptions /
   constraints on the attacker (i.e., the attacker can use the best
   available attack techniques) except perhaps that the attacker only
   utilize a polynomial amount of resources.  The security assumptions
   are often simpler (e.g., eavesdropping only, or eavesdropping plus
   network packet injection).

   Good systems security mechanisms must also make it less likely for
   an attacker to succeed.  However, systems being complex entities,
   there will be multiple points of vulnerability, and attackers will
   penetrate the systems at their weakest link.

   Discuss StackGuard, RaceGuard, and AEGIS in this context,
   addressing:

   A. What are their threat models?  What do their threat models leave
   out?

   B. How hard would it be for an attacker to bypass their security
   mechanism(s)?  Discuss possible ways of doing so.

   C. Do these mechanisms reduce the (unconstrained) attackers'
   success probabilities?  Are they worthwhile?

   D. Is reasoning about system security using a probabilistic model
   the correct approach?  Explain why or why not.

2. Read the pre-print of a paper at

   ftp://www.cs.ucsd.edu/pub/bsy/pub/monotonicity-preprint.ps
   
   Discuss:

   A. What is the threat model?  What does the threat model leave out?

   B. How different is the state transition inconsistency detection
   from an intrusion detection system?  Discuss similarities and
   differences.

   C. Does this scheme work synergistically/antagonistically with the
   ideas in the Authentication and State Appraisal paper?  Assuming
   you need to use mobile agents, do these schemes reduce the
   (unconstrained) attackers' success probabilities?  Would these
   schemes be worthwhile?