| 1. |
- Jonsson, Erland, 1946, et al.
(författare)
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A Dependability Measure for Degradable Computing Systems
- 1992
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper deals with the problem of finding a comprehensive dependabilitymeasure or figure of merit for computing systems. Dependability is a term usedfor a general description of a systems trustworthiness in non-quantitative terms. Itis commonly described by a number of aspects, like reliability, availability, safetyand security. Quantitative measures are conveniently used for e.g. reliability andavailability, but are rare for security.However, it is felt that a more general measure of a system’s dependability wouldbe of great interest and could be used for system evaluations, design trade-offs etc.In order to achieve this, we adopt a generalized view that facilitates a recompilationof the dependability aspects into fewer and more general qualities. Key issues forthe generalization are the concepts of degradability and service. A degraded serviceis the result of the discontinuation of one or several subservices, yielding a systemthat operates on a reduced service level.A vectorized measure based on Markov processes is suggested, and mathematicaldefinitions are given. The measure describes the expected time a system willbe operating at a certain service level, and also the probability that this level bereached. By means of applying the concept of reward rate to each service level, aneven more simplified figure of merit can be calculated.Normally, when making reliability calculations, an assumption of exponentialfailure rates for system components is made. Sometimes this assumption is notrealistic and we outline how phase-type distributions can be used to cope with thissituation.Finally, two different schemes for the calculation of the measure is given. First,a hierarchical procedure feasible for small systems and calculations by hand is presented.Second, a general procedure based on matrix calculus is given. This procedureis suitable for complicated systems. It is also general in the sense that it maybe used for measures extended to repairable systems.
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| 3. |
- Brocklehurst, Sarah, et al.
(författare)
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On measurement of operational security
- 1994
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Ingår i: IEEE Aerospace and Electronic Systems Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8985. ; 9:10, s. 7-16
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Tidskriftsartikel (refereegranskat)abstract
- Ideally, a measure of the security of a system should capture quantitatively the intuitive notion of "the ability of the system to resist attack." That is, it should be operational, reflecting the degree to which the system can be expected to remain free of security breaches under particular conditions of operation (including attack). Instead, current security levels at best merely reflect the extensiveness of safeguards introduced during the design and development of a system. Whilst we might expect a system developed to a higher level than another to exhibit "more secure behavior" in operation, this cannot be guaranteed; more particularly, we cannot infer what the actual security behavior will be from knowledge of such a level. In the paper we discuss similarities between reliability and security with the intention of working toward measures of "operational security" similar to those that we have for reliability of systems. Very informally, these measures could involve expressions such as the rate of occurrence of security breaches, or the probability that a specified "mission" can be accomplished without a security breach. This new approach is based on the analogy between system failure and security breach, but it raises several issues which invite empirical investigation. We briefly describe a pilot experiment that we have conducted to judge the feasibility of collecting data to examine these issues.
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| 4. |
- Jonsson, Erland, 1946, et al.
(författare)
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On the Integration of Security and Dependability in Computer Systems
- 1992
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Ingår i: IASTED International Conference on Reliability, Quality Control and Risk Assessment Washington DC, USA, 1992, ISBN 0-88986-171-4. ; , s. 93-97
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Konferensbidrag (refereegranskat)abstract
- Historically the trustworthiness of a computer system was characterized by its reliability and availability. Later on safety was integrated into what is now termed dependability. System security was originally a concept that described the protection of information from intentional and hostile interaction. It has now been suggested that security should be treated as a dependability attribute, parallel to reliability, availability and safety, but the implications of this integration has not yet been fully realized. This paper presents a novel approach to security, intended to facilitate and improve this integration. This is accomplished by taking a dependability viewpoint on traditional security and interpreting it in terms of system behaviour and fault prevention. A modified security concept, comprising only fault prevention characteristics and a new behaviouristic concept, privacy, are defined. The outcome of this interpretation will influence the integration of the other three dependability attributes.
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| 5. |
- Olovsson, Tomas, 1959
(författare)
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A Structured Approach to Computer Security
- 1992
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Security and dependability are two closely connected areas. Recently, some attempts have been made to integrate the two concepts by integrating security into the more general topic of dependability. This paper describes security concepts and gives a survey of security terminology. It also establishes a taxonomy reflecting concepts within the security area which enables the integration of security and dependability. Special concern is given to the problems which inevitably arise from the integration, for example, a somewhat different definition of security is introduced. This paper does not pretend to cover every single mechanism found in security, but is rather an attempt to create a taxonomy for security analysis, estimation and design; a taxonomy that should be useful for further research within this area.
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| 6. |
- Bengtsson, Lars, 1958-, et al.
(författare)
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A processor array module for distributed, massively parallel, embedded computing
- 1993
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Ingår i: Microprocessing and Microprogramming. - Amsterdam : Elsevier. - 0165-6074. ; 38:1-5, s. 529-537
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Tidskriftsartikel (refereegranskat)abstract
- With the increased degree of miniaturization resulting from the use of modem VLSI technology and the high communication bandwidth available through optical connections, it is now possible to build massively parallel computers based on distributed modules which can be embedded in advanced industrial products. Examples of such future possibilities are ''action-oriented systems'', in which a network of highly parallel modules perform a multitude of tasks related to perception, cognition, and action. The paper discusses questions of architecture on the level of modules and inter-module communication and gives concrete architectural solutions which meet the demands of typical, advanced industrial real-time applications. The interface between the processors arrays and the all-optical communication network is described in some detail. Implementation issues specifically related to the demand for miniaturization are discussed.
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