Quiz 2 (Total: 15), Oct 4, 2011
Name:
1.
Let
x
and
y
be subjects,
z
a subject or object, and
r
be a
read
right. Write the
following access control command that captures the
take
rule of the TakeGrant
model. Assume that an access control matrix
A
contains the rights specified in a
TakeGrant graph.
command
take_right
(
x
,
y
,
z
,
r
):
x
takes right
r
over
z
from
y
, provided
x
has
take
right over
y
,
and
y
has
r
right over
z
.
Answer
:
command
take_right
(
x
,
y
,
z
,
r
)
if (
take
a
[
x, y
]) and (
r
a
[
y, z
])
then Enter
r
in
a
[
x, z
]
end
2.
Write
T
for
True
or
F
for False
[F ]
Biba’s
integrity model
can be used to prevent spread of viruses.
[T ]
Implementation of the BLP model is difficult because of the problems
related to
polyinstantiation
and
covert channels
.
[T ]
The
reduction
of the
Turing Machine Halting Problem
to the
Safety
Problem
means that if the
Safety Problem
was decidable then the
Turing
Machine Halting Problem
would also have been decidable.
Assume that an object
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 Fall '11
 Joshi
 Halting problem, Alan Turing

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