Protection matrix
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and the context of each cell determines what operations on a particular object are permitted for a particular subject. | and the context of each cell determines what operations on a particular object are permitted for a particular subject. | ||
- | == | + | == An artificial example == |
If: | If: | ||
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[[Image:Protection matrix1.png]] | [[Image:Protection matrix1.png]] | ||
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+ | The matrix determines which operations (R = read, W = write, X = execute) with particular objects are allowed for particular subjects. | ||
It is not very usual to actually store permissions in the form of a 2-dimensional array as shown in the figure above but there are such systems which do so. Usually, the set of subjects and the set of objects are small and immutable. | It is not very usual to actually store permissions in the form of a 2-dimensional array as shown in the figure above but there are such systems which do so. Usually, the set of subjects and the set of objects are small and immutable. | ||
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+ | == Real world examples == | ||
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+ | * [[Protection matrixes in Minix]] |
Latest revision as of 09:08, 8 September 2009
Definition
One way how to capture the permissions of subjects to perform various operations with objects is to use a large matrix where:
- rows correspond to particular subjects
- columns correspond to particular objects
and the context of each cell determines what operations on a particular object are permitted for a particular subject.
An artificial example
If:
- we have only three different subjects (1, 2 and 3)
- eight different objects (six files and a printer and a mixer)
- we recognize three different operations with objects (read, write and execute)
then one possible protection matrix may be:
The matrix determines which operations (R = read, W = write, X = execute) with particular objects are allowed for particular subjects.
It is not very usual to actually store permissions in the form of a 2-dimensional array as shown in the figure above but there are such systems which do so. Usually, the set of subjects and the set of objects are small and immutable.