midterm05 - IS-2150/TEL-2810 Introduction to Computer...

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1 IS-2150/TEL-2810 Introduction to Computer Security Midterm, Tuesday, Oct 12, 2005 Name: Email: Total Time : 2:30 Hours Total Score : 100 There are total of 12 questions. Note that scores for each question may be different – so spend time accordingly on each question . Be precise and clear in your answers Score Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12
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2 Part 1 1. Mathematical foundation [5+5] 1. Give the logical expression for the following statement a. Not all birds can fly Answer: b. Every directory contains some files Answer: 2. Prove by induction the following M(n) : ( )( ) 222 2 12 1 1 2 3 ... 6 nn n n + + +++ += Answer:
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3 2. Write T for true and F for false for the following statements: [10] [ ] Security usually is based on assumptions specific to the type of environment. [ ] Information flow problem occurs only when unauthorized access is allowed. [ ] One of the organizational problems in security is the question of who is responsible for the security of the computers. [ ] In some systems (like Unix), if a subject s is owner of object o , then even if s has no read or write right over o , s may give read or write right over o to another subject. This, however, does not violate the principle of attenuation of privilege . [ ] One way to prove that a given problem is undecidable is to reduce it to the Turing machine’s halting problem. [ ] In originator controlled access control, the owner of a file has no control over who may access the file. [ ] In a mandatory access control model, a system mechanism controls access to an object and an individual user can occasionally alter that access. [ ] Assume than any intrusion to a system eventually transitions the system state to an insecure state. If you install an intrusion prevention mechanism which ensures that only known intrusions to the system are blocked, the intrusion prevention mechanism is precise .
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midterm05 - IS-2150/TEL-2810 Introduction to Computer...

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