ha7_11sol - CIS 4360 Introduction to Computer Security –...

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Unformatted text preview: CIS 4360 Introduction to Computer Security – with answers Home Assignment 7, Fall 2011 Due: Tue 9:30pm, 11/1/2010 This concerns Security models . Examples taken from: Dieter Gollmann, Computer Security, 2nd Edition, John Wiley. 1. What does “ tranquility ” mean in the BLP model. Answer. The tranquility principle limits the applicability of BLP to systems where security levels do not change dy- namically. It allows controlled copying from high security levels to low security levels via trusted subjects. More specifically, the tranquility principle of the BLP model states that the classification of a subject or ob- ject does not change while it is being referenced. There are two forms to the tranquility principle: “strong tranquility” for which the security levels do not change during the normal operation of the system; “weak tranquility” for which the security levels may never change in such a way as to violate a defined security policy (of BLP). Weak tranquility is desirable as it allows systems to observe the principle of least privilege. That is,(of BLP)....
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This document was uploaded on 12/04/2011.

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