HW2 - + n n 2) D o t h e f o l l o w i n g [25 Points] i)...

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IS2150/TEL2810 Introduction to Security Homework 2 Total Points: 50 Due Date: September 29, 2009 1) Exercise on Propositional/Predicate logic [25 Points] (a) Prove that A B ( ¬ A B) (A ∧¬ B) (use the truth table) (b) Express the following sentences in propositional//first order logic. Be sure to define all propositional components (e.g., predicate function, constants, and variables). i) If it does not rains we will go to the Steeler’s game. ii) If a subject has Secret clearance then he/she is allowed to write all Top Secret and Secret files. iii) A person can approve a check or cash it but cannot do both . iv) A directory is older than the directories and the files that it contains. (c) Prove by using Induction the following 1 3 = 2 3 + 3 3 + … + n 3 = 2 2 ) 1 (
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Unformatted text preview: + n n 2) D o t h e f o l l o w i n g [25 Points] i) Describe and differentiate between the mechanisms related to: Setuid program in Unix and Impersonation in Windows ii) Note that the following two resolution rules are used in Windows. Explain how given a security descriptor and an access token , these resolution techniques are used. (1) Positive permissions are additive (2) Negative permission (deny access) takes priority iii) Assume that when a file is created and before the umask value has been applied, the permission bits are 0626 (in class we assumed 0777). What will be the permission setting for the new files when the following umask values are applied (1) 032 (2) 031 (3) 051...
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