Suppose that a system has $1000$ objects and $100$ domains at some time. $1\%$ of the objects are accessible $($some combination of $r,w$ and $x)$ in all domains,

$10\%$ are accessible in two domains, and the remaining $89\%$ are accessible in only one domain. Suppose one unit of space is required to store an access right

$($some combination of $r,w,x),$ object ID$,$ or a domain ID$.$ How much space is needed to store the full protection matrix, protection matrix as ACL, and protection

matrix as capability list?

Explain which implementation of the protection matrix is more suitable for the following operations:

a$.$ Granting read access to a file for all users.

b$.$ Revoking write access to a file from all users.

c$.$ Granting write access to a file to John, Lisa, Christie, and Jeff.

d$.$ Revoking execute access to a file from Jana, Mike, Molly, and Shane.

Suppose there are three security levels, $1,2,$ and $3.$ Objects A and B are at level $1,C$ and $D$ are at level $2,$ and $E$ and $F$ are at level $3.$ Processes $1$ and $2$ are

at level $1,3$ and $4$ are at level $2,$ and $5$ and $6$ are at level $3.$ For each of the following operations, specify whether they are permissible under Bell$-$LaPadula

model, Biba model, or both.

a$.$ Process $1$ writes object $D$

b$.$ Process $4$ reads object $A$

c$.$ Process $3$ reads object $C$

d$.$ Process $3$ writes object $C$

e$.$ Process $2$ reads object $D$

f$.$ Process $5$ writes object $F$

g$.$ Process $6$ reads object $E$

h$.$ Process $4$ write object $E$

i$.$ Process $3$ reads object $F$