Sandhu, R.S. "Undecidability of the Safety Problem for The Schematic Protection Model with Cyclic Creates." Journal of Computer and System Sciences, in press. Home/Search Document Not in Database Summary Related Articles Check |
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The Typed Access Matrix Model - Sandhu (1992) (34 citations) Self-citation (Sandhu) (Correct)
....to be of a particular type which thereafter does not change. z In this paper we define the typed access matrix (TAM) model by introducing the notion of strong typing into HRU. We prove that monotonic TAM (MTAM) has strong safety properties similar to those of Sandhu s Schematic Protection Model [21, 22], and its recent extension by Ammann and Sandhu to Extended SPM (ESPM) 2, 3, 4] Second we show how safety can be made tractable, y We assume that the authorization scheme is enforced by a high assurance reference monitor. If the reference monitor can be bypassed there is, of course, no basis ....
....only if (u; v) 2 cc. Visualize the cc relation as a directed graph, called the cc graph, whose vertices are the types with an edge from u to v if and only if (u; v) 2 cc. SPM has decidable safety provided the cc graph is acyclic [21] whereas with arbitrary cycles in cc safety is undecidable [22]. Moreover, in the special case of loops (i.e. cycles of length one which allow a subject to create subjects of its own type) safety remains decidable if an additional requirement known as attenuating is imposed. Useful security policies do not appear to require arbitrary cycles in the cc graph. ....
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Sandhu, R.S. "Undecidability of the Safety Problem for The Schematic Protection Model with Cyclic Creates." Journal of Computer and System Sciences, in press.
Expressive Power of the Schematic Protection Model - Sandhu (1992) (4 citations) Self-citation (Sandhu) (Correct)
....types. In particular, subject creation is authorized by a can create binary relation on types. Safety is decidable provided this relation is acyclic, and in certain cases even if it has cycles of length one [34] On the other hand with arbitrary cycles in can create, safety is undecidable [38]. Fortunately, it appears that SPM schemes of practical interest satisfy the decidability constraints, as demonstrated by the constructions of this paper and the examples of [32, 33, 34, 36] Our objective in this paper is to demonstrate that SPM subsumes several wellknown protection models as ....
....type, there is no difference between them as far as the scheme is concerned. So for purpose of safety analysis it suffices to create just one of them. Of course if cc has cycles the above procedure will not terminate. Indeed it has been shown that with arbitrary cycles in cc safety is undecidable [38]. So there is no algorithm for computing a suitable augmented state in general. For the most part it appears that cycles in cc do not arise in practice. In our experience cycles in cancreate occur only in the very special, but also very important, case where a subject is authorized to create new ....
Sandhu, R.S. "Undecidability of the Safety Problem for The Schematic Protection Model with Cyclic Creates." Journal of Computer and System Sciences, in press.
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