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How to prevent type flaw attacks on security protocols

Journal of Computer Security 2003年第2期11卷 217-244页

作者： Heather, James Lowe, Gavin Schneider, Steve Department of Computing School of Electronics Computing and Mathematics University of Surrey Guildford Surrey GU2 7XH UK. E-mail: Programming Research Group Oxford University Computing Laboratory Wolfson Building Parks Road Oxford OX1 3QD UK. E-mail: Royal Holloway University of London Egham Hill Egham Surrey TW20 0EX UK. E-mail:

A type flaw attack on a security protocol is an attack where a field that was originally intended to have one type is subsequently interpreted as having another type. A number of type flaw attacks have appeared in the academic literature. In this paper we prove that type flaw attacks can be prevented using a simple technique of tagging each field with some information indicating its intended type.

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Managing external workload with BSP time warp

Managing external workload with BSP time warp

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Proceedings of the 2002 Winter Simulation Conference

作者： Low, Malcolm Yoke Hean Programming Research Group Computing Laboratory University of Oxford Parks Road Oxford OX1 3QD United Kingdom

An extension to the existing bulk synchronous parallel time warp (BSP-TW) dynamic load-balancing algorithms was presented. The algorithm allowed the management to work without interruption from external workload. Experiments results on a manufacturing simulation model showed that significance performance improvement could be achieved with external workload management.

关键词： Parallel processing systems

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Quantitative program logic and expected time bounds in probabilistic distributed algorithms

Quantitative program logic and expected time bounds in proba...

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Real Time and Probabilistic Systems (ARTS '99)

作者： McIver, A.K. Programming Research Group Oxford University Computing Laboratory Wolfson Building Parks Road Oxford OX1 3QD United Kingdom

In this paper we show how quantitative program logic (Morgan et al., ACM Trans. programming Languages Systems 18 (1996) 325) provides a formal framework in which to promote standard techniques of program analysis to a context where probability and nondeterminism interact, a situation common to probabilistic distributed algorithms. We show that overall expected time can be formulated directly in the logic and that it can be derived from local properties of components. We illustrate the methods with an analysis of expected running time of the probabilistic dining philosophers (Lehmann and Ravin, Proc 8th Annu. ACM. Symp. on principles of programming Languages, ACM, New York, 1981, p. 133). © 2002 Published by Elsevier Science B.V.

关键词： Probabilistic logics

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Managing external workload with BSP Time Warp

Managing external workload with BSP Time Warp

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Simulation Winter Conference

作者： M.Y.H. Low Programming Research Group Computing Laboratory University of Oxford Oxford UK

This paper describes an extension to the existing BSP Time Warp (Bulk Synchronous Parallel Time Warp) dynamic load-balancing algorithm to allow the management of interruption from external workload. Experiments carried out on a manufacturing simulation model using different partition strategies with and without interruption from external workload show that significant performance improvement can be achieved with external workload management.

关键词： Computational modeling Protocols Virtual manufacturing Heuristic algorithms Concurrent computing Time warp simulation Costs Laboratories Partitioning algorithms Interference

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Dynamic load-balancing for BSP Time Warp

Dynamic load-balancing for BSP Time Warp

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Annual Symposium on Simulation

作者： M.Y.H. Low Programming Research Group Computing Laboratory University of Oxford Oxford UK

The performance of a parallel simulation system depends very much on partitioning simulation workload evenly among the set of processors in the computing environment to ensure load-balance between processors. Most parallel simulation systems employ user-defined static partitioning. However static partitioning requires in-depth domain knowledge of the specific simulation model in the study. It is not effective if the workload of a simulation model could not be quantified accurately or changes over time during a simulation run. Dynamic load-balancing allows the simulation system to automatically balance the workload of different simulation models without user's input. In this paper the use of dynamic load-balancing in the context of the BSP Time Warp optimistic protocol is examined. Based on the BSP cost model, a dynamic load-balancing algorithm for the BSP Time Warp protocol is developed. Using different simulation models, the paper shows that to achieve consistent performance, the dynamic load-balancing algorithm for BSP Time Warp needs to consider both computation and communication workload, as well as lookaheads between processors.

关键词： Computational modeling Costs Protocols Concurrent computing Heuristic algorithms Time warp simulation Computational efficiency Algorithm design and analysis Parallel programming Load modeling

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Accuracy of profile maintenance in optimizing compilers

Accuracy of profile maintenance in optimizing compilers

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Annual Workshop on Interaction between Compilers and Computer Architectures

作者： Youfeng Wu Programming Systems Research Laboratory Intel Corporation Santa Clara CA USA

ISBN: (纸本)0769515347

Modern processors rely heavily on optimizing compilers to deliver their performance potentials. The compilers, in turn, rely greatly on profile information to focus the optimization efforts and better match the generated code with the target machines. Maintaining the profile in an optimizing compiler is important as many optimizations can benefit from profile information and they are often performed one after the other. Maintaining a profile is, however, tedious and error prone. An erroneous profile is not easy to detect as it affects only the performance, not the correctness, of a program. Maintaining a profile also inherently loses accuracy, as the profile update operations often have to use probabilistic approximation. In this paper, we measure the accuracy of maintaining CFG profiles in a high-performance optimizing compiler. Our data indicates that the compiler maintains the profile more accurately within individual functions than globally across functions, and function inlining may be responsible for the loss of profile accuracy globally. We also identify a number of research issues related to profile maintenance.

关键词： Optimizing compilers Frequency Flow graphs Educational institutions Productivity programming profession Automatic control Conferences Computer architecture

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Weakest specifunctions for BSP

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Parallel Processing Letters 2001年第4期11卷 439-454页

作者： Chen, Yifeng Sanders, J.W. Department of Maths and Computer Science University of Leicester University Road Leicester LE1 7RH United Kingdom Programming Research Group Oxford University Computing Laboratory Parks Road Oxford OX1 3QD United Kingdom

This paper introduces a calculus of weakest specification for supporting reuse of established components in deriving a design (in the sense of formal methods). The weakest specifunction generalizes the notions of weakest pre-specification and weakest parallel environment;but instead of calculating the weakest required component of a target specification, it calculates the weakest specification function whose value refines the target when applied to an established component. In particular it overcomes the restriction of those other calculi to taking merely one required component at a time. The theory of specifunctions is applied to a new weakest-design calculus in the context of BSP. The calculus is based on the par-seq specifunction which involves two required components: it places one established component in parallel with one required component and the result in sequence with another required component to meet a given specification. A calculus is provided for the par-seq specifunction and it is applied to the derivation of a distributed BSP algorithm for greatest common divisor.

关键词： Parallel processing systems

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Consistent modeling of distributed mutual exclusion protocol using optimistic simulation 01

Consistent modeling of distributed mutual exclusion protocol...

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Proceedings of the fifteenth workshop on Parallel and distributed simulation

作者： Malcolm Yoke Hean Low David M. Nicol Programming Research Group Computing Laboratory University of Oxford Dept. of Computer Science Dartmouth College

ISBN: (纸本)9780769511047

This paper discusses the problem of risk in optimistic simulation protocols, using as example simulation of a distributed mutual exclusion protocol with strong consistency properties. The simulation model is augmented to detect model inconsistency errors resulting from risky optimistic simulation. While the model runs sequentially without consistency errors, errors occur when the model is executed in parallel optimistically. Some of the errors entirely violate the fundamental mutual exclusion properties of the model itself. To address this problem we extend the optimistic simulation library to eliminate these inconsistencies. We discuss the details of these extensions and the performance trade-off for adding them.

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Consistent modeling of distributed mutual exclusion protocol using optimistic simulation

Consistent modeling of distributed mutual exclusion protocol...

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Workshop on Principles of Advanced and Distributed Simulation (PADS)

作者： M.Y.H. Low D.M. Nicol Programming Research Group Computing Laboratory University of Oxford UK Department of Computer Science Dartmouth College USA

ISBN: (纸本)076951104X

This paper discusses the problem of risk in optimistic simulation protocols, using as an example, simulation of a distributed mutual exclusion protocol with strong consistency properties. The simulation model is augmented to detect model inconsistency errors resulting from risky optimistic simulation. While the model runs sequentially without consistency errors, errors occur when the model is executed in parallel optimistically. Some of the errors entirely violate the fundamental mutual exclusion properties of the model itself. To address this problem, we extend the optimistic simulation library to eliminate these inconsistencies. We discuss the details of these extensions and the performance tradeoff for adding them.

关键词： Protocols Computational modeling Libraries Hazards Computer simulation Laboratories Computer science Educational institutions Computer errors Parallel processing

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Reducing noise in gossip-based reliable broadcast

Reducing noise in gossip-based reliable broadcast

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Reliable Distributed Systems

作者： P. Kouznetsov R. Guerraoui S.B. Handurukande A.-M. Kermarrec Distributed Programming Laboratory Swiss Federal Institute of Technology Lausanne Switzerland Microsoft Research Limited Cambridge USA

We present in this paper a general garbage collection scheme that reduces the "noise" in gossip-based broadcast algorithms. In short, our garbage collection scheme uses a simple heuristic to trade "useless" messages with "useful" ones. Used with a given gossip-based broadcast algorithm, a given size of buffers, and a given number of disseminated messages (e.g., per gossip round), our garbage collection scheme provides higher overall reliability than more conventional schemes. We illustrate our approach through two algorithms: bimodal multicast (pbcast) and lightweight probabilistic broadcast (lpbcast). Our scheme is based on the intuitive idea of discarding messages according to their "age". The "age" of a message represents the number of times the message has been retransmitted.

关键词： Noise reduction Broadcasting Multicast algorithms Scalability Laboratories Broadcast technology Local area networks Degradation Redundancy Large-scale systems

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