SHW2 - IS2150/TEL2810 Introduction to Security Homework 2...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: IS2150/TEL2810 Introduction to Security Homework 2 Total Points: 50 1) Exercise on Propositional/Predicate logic [25 Points] (a) Prove that A B (A B) ( A B) (you can use the truth table) (5 points) (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 rain we will go to the Steelers game. (3 points) R = it rains S = go to Steelers game R S ii) If a subject has Secret clearance then he/she is allowed to write to Secret and Top Secret files (3 points) SecretSubject(x) = subject x has secret clearance TopSecretFile(f) = file f is top secret SecretFile(f) = file f is secret allowWrite(x, y) = subject x is allowed to write to file y x f [ SecretSubject(x) ((SecretFile(f) TopSecretFile(f)) canWrite(x,f) ) ] iii) A person can approve a check or cash it but cannot do both. (3 points) canApprove(x, c) = x can approve check c canCash(x, c) = x can cash check c x, c [ (canApprove (x, c) canCash(x, c)) (canCash(x, c) canApprove(x, c)) ] iv) A directory is older than the directories and the files that it contains. (4 points) isOlder(x, y) = x is older than y isDirectory(x) = x is a directory isFile(x) = x is a file Contains(x, y) = x contains y...
View Full Document

This note was uploaded on 11/02/2009 for the course SIS 2150 taught by Professor Joshi during the Spring '09 term at Philadelphia.

Page1 / 3

SHW2 - IS2150/TEL2810 Introduction to Security Homework 2...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online