Given security levels (Top Secret, Secret, Classified, Unclassified) and that To

Question

Given security levels (Top Secret, Secret, Classified, Unclassified) and that Top Secret > Secret > Classified > Unclassified that can be assigned to subjects who need to be controlled access to objects that may contain data of categories {A, B, C}. User can be given READ, WRITE, READ+WRITE, NONE type of access to the objects. Assuming that the system implements the Discretionary or Simple-Policy, as defined by the Bell-La Padula model, what type access will granted for the cases listed below:

a) Alice is cleared for (Top Secret, {A, C} ) and wants to access a document classified as (Secret, {B, C})   

b) Bob is cleared for (Secret, {A}) wants to access (Secret, {B})

c) Claire is cleared for (Top Secret, {A, C}} and wants to access a document classified as ( Confidential, {A, C})   

d) Dave is cleared for (Secret, {A, B}) and wants to access a document classified as (Top Secret, {A} )

e) Elsa has UNCLASSIFIED designation and wants access a document classified as (Confidential, {A} )

Explanation / Answer

Let A’s compartment be (LA, CA) and B’s be (LB, CB). The simple security condiion says that A can read B if and only if LA LB and CB CA. The *-property says that A can write B if and only if LB LA and CA CB. Remember that TOPSECRET SECRET CONFIDENTIAL UNCLASSIFIED

a. LAlice= TOPSECRET SECRET = Ldoc, so Paul cannot write the document. Paul cannot read the document either, because Cdoc = { B, C } { A, C } = CPaul.

b. LBob = CONFIDENTIAL CONFIDENTIAL = Ldoc, but Cdoc = { B } { C } = CAnna so Anna cannot read the document, and CAnna = { C } { B } = Cdoc, so Anna cannot write the document.

c. LClaire = SECRET CONFIDENTIAL = Ldoc, and Cdoc = { C } { C } = CJesse, so Jesse can read the document. As LJesse > Ldoc, however, Jesse cannot write the document.

d. As LDave= TOPSECRET CONFIDENTIAL = Ldoc andCdoc = { A} { A, C } = CSammi, Sammi can read the document. But the first inequality means Sammi cannot write the document.

e. As C Elsa = { B } = Cdoc and Ldoc = CONFIDENTIAL UNCLASSIFIED = LRobin, Robin can write the document. However, because Ldoc LRobin, she cannot read the document.

2. Would raising the classification of an object violate any properties of the BellLaPadula model? Why or why not?

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