CS 526 Information Security Assignment 4 John Ross Wallrabenstein jwallrab October 1 2010 6 2 6 Problem 2 2 1 a True 2 2 6 b We assume that in order to support verification of refers to the ability to ascertain whether or not the integrity and confidentiality of the system still hold We are not addressing whether or not availability is more important than integrity or confidentiality as that would depend on the particular system under consideration Additionally we are not addressing whether or not integrity or confidentiality can be supported without availability as the question specifically pertains to the verification of integrity or confidentiality Finally we do not consider verification to include the assumption that if there is no availability whatsoever and the system s integrity confidentiality was not violated prior to the loss of all availability you can verify they are still in tact because no one could access them We consider verification to explicitly mean that the data is accessed in some way to verify neither integrity nor confidentiality have been compromised This statement under the above assumptions is clearly true That is it is impossible to verify the integrity or confidentiality of a system if the system is unavailable That is some degree of availability must be present or no user can access the system to verify that its integrity or confidentiality has not been compromised 3 3 1 Problem 3 Release Write Definition The release write rule enables a subject s to request to release the right to write an object o Represent this request as r release s o w R 1 and let the current state of the system be v b m f h Then release write is the rule 1 r v Algorithm 1 Release Write if r 1 then 1 r v i v else 1 r v y b s o w m f h end if Theorem 3 1 The release write rule 1 preserves the simple security condition the property and the ds property Lemma 3 2 The release write rule 1 preserves the simple security condition security condition is satisfied because v satisfies the condition If b 6 b then s o w b and we have that b b As v satisfies the simple security condition all rules in b must also satisfy the simple security condition Thus b b and f f implies that v will also satisfy the simple security condition Lemma 3 3 The release write rule 1 preserves the property Proof Let v satisfy the property and let 1 r v d v Either v v or v b s o w m f h by the release write rule When v v we have that v satisfies the property because v does In the latter case we have v b s o w m f h For either choice of v we have that b b That is if v v then b b and the property is satisfied because v satisfies the property If b 6 b then s o w b and we have that b b As v satisfies the property all rules in b must also satisfy the property Thus b b and f f implies that v will also satisfy the property Lemma 3 4 The release write rule 1 preserves the ds property Proof Let v satisfy the ds property and let 1 r v d v Either v v or v b s o w m f h by the release write rule When v v we have that v satisfies the dsproperty because v does In the latter case we have v b s o w m f h For either choice of v we have that b b That is if v v then b b and the ds property is satisfied because v satisfies the property If b 6 b then s o w b and we have that b b As v satisfies the ds property all rules in b must also satisfy the ds property That is we have m s o m s o s S o O Thus v will also satisfy the ds property Proof Let v satisfy the simple security condition and let 1 r v d v Either v v or v b s o w m f h by the release write rule When v v we have that v satisfies the simple security condition because v does In the latter case we have v b s o w m f h As we have shown that release write preserves For either choice of v we have that b b the simple security condition property and dsThat is if v v then b b and the simple property we have proven Theorem 3 1 3 2 Rescind Execute Proof Let v satisfy the property and let 2 r v d v Either v v or v Definition The rescind execute rule enables a b s o e m s o e f h by the rescind subject s to request to rescind subject s s right execute rule When v v we have that v satto execute an object o Represent this request as isfies the property because v does In the latr s r s o e and let the current state of ter case we have v b s o e m s o the system be v b m f h Then rescind e f h Either b b or b b s o e execute is the rule 2 r v If b b then b b and f 0 f so v satisfies the property because v satisfies the property Algorithm 2 Rescind Execute If b 6 b then b b s o e This imif r 2 then plies that b b and f f so v satisfies the 2 r v i v property because v satisfies the property else if r 2 o 6 root o parent o 6 root o parent o b s w parent o Lemma 3 8 The rescind execute rule 2 preroot o canrescind s o v o root o serves the ds property canrescind s root o v then 2 r v y b s o e m m s o Proof Let v satisfy the ds property and let 2 r v d v Either v v or v e f h b s o e m s o e f h by the rescindelse execute rule When v v we have that v sat 2 r v n v isfies the ds property because v does In the latend if ter case we have v b s o e m s o e f h For either choice of v we have that b b That is if v v then b b and Theorem 3 5 The rescind execute rule 2 prethe ds property is satisfied because v satisfies the serves the simple security condition the property If b 6 b then s o e b and we property and the ds property have that b b As v satisfies the ds property all …