Homework 4

Due: November 22, 2022
Points: 100

1. (30 points) Discuss controls that would prevent Dennis Ritchie’s bacterium (see Section 23.6.1) from absorbing all system resources and causing a system crash.

2. (30 points) Consider the statement

   
   if (x = 1) and (y = 1) then z := 1 
   

   where x and y can each be 0 or 1, with both equally likely and z is initially 0. Compute the conditional entropies H(x | z′) and H(y | z′), where z′ is the value of z after the statement is executed.

3. (40 points) Extend the semantics of the information flow security mechanism in Section 17.3.1 to include structures (sometimes called “records”).

Matt Bishop Office: 2209 Watershed Sciences Phone: +1 (530) 752-8060 Email: mabishop@ucdavis.edu

ECS 235A, Computer and Information Security Version of November 17, 2022 at 2:44PM

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