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Computer

Issue 2 • Date Feb. 1991

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Displaying Results 1 - 6 of 6
  • Pseudorandom bit generators in stream-cipher cryptography

    Page(s): 8 - 17
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    Progress in the design and analysis of pseudorandom bit generators over the last decade is surveyed. Background information is provided, and the linear feedback shift registers that serve as building blocks for constructing the generators are examined. Three methods for attacking keystream generators are reviewed, and three techniques for designing them are considered, focusing on how they fail or how their weakness is exposed under the attacks previously described. These techniques are nonlinear feedforward transformation, step control, and multiclocking.<> View full abstract»

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  • A comparative evaluation of expert system tools

    Page(s): 19 - 31
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1396 KB)  

    The results of an assessment of the functionality and performance of tools with different architectural approaches are presented. The goal was to gain insight into the advantages and disadvantages of the various architectures. The tools evaluated in the study were (1) the Automated Reasoning Tool for Information Management (ARTIM), (2) the C Language Integrated Production System (CLIPS), (3) the Knowledge Engineering System (KES), (4) Level 5, and (5) VAX OPS5. Emphasis was on tools implemented in languages other than Lisp. KES and Level 5 were found to be inadequate for an application that required constructive problem solving, but both tools could be expected to provide improved performance for problems based on a heuristic classification approach due to their backward-chaining orientation. On the other hand, ART-IM, CLIPS, and VAX OPS5 might prove less effective for heuristic classification problem solving than for synthesis because they lack support for backward chaining. The results reinforce the fact that all expert system tools have strengths and weaknesses and that no single tool is dominant for a wide spectrum of applications or over a wide range of functionality.<> View full abstract»

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  • Paradigm: a highly scalable shared-memory multicomputer architecture

    Page(s): 33 - 46
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1614 KB)  

    Paradigm (parallel distributed global memory), a shared-memory multicomputer architecture that is being developed to show that one can build a large-scale machine using high-performance microprocessors, is discussed. The Paradigm architecture allows a parallel application program to execute any of its tasks on any processor in the machine, with all the tasks in a single address space. The focus is on novel design techniques that support scalability. The key performance issues are identified, and some results to date from this work and experience with the VMP architecture design on which it is based are summarized.<> View full abstract»

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  • Identifying and qualifying reusable software components

    Page(s): 61 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1022 KB)  

    Identification and qualification of reusable software based on software models and metrics is explored. Software metrics provide a way to automate the extraction of reusable software components from existing systems, reducing the amount of code that experts must analyze. Also, models and metrics permit feedback and improvement to make the extraction process fit a variety of environments. Some case studies are described to validate the experimental approach. They deal with only the identification phase and use a very simple model of a reusable code component, but the results show that automated techniques can reduce the amount of code that a domain expert needs to evaluate to identify reusable parts.<> View full abstract»

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  • Integrated voice-data communication over high-speed fiber optic networks

    Page(s): 49 - 58
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1080 KB)  

    Voice-data integration over emerging high-speed fiber-optic LANs and MANs employing unidirectional buses for information transfer is addressed. Packet voice characteristics and requirements are examined, as are the characteristics of fiber-optic networks. Both train-oriented and non-train-oriented protocols are discussed and compared.<> View full abstract»

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  • Standards-ethics and the safety of computer systems

    Page(s): 72 - 75
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    The issue of responsibility for computer failures in critical systems is addressed, taking medical information systems as an example. Three basic modes of ethical analysis are defined and used to analyze the ethical questions raised for such systems. The first, called normative ethics, seeks to develop and justify rules for right conduct. The second, called the ethics of virtue, asks what kind of person does the right thing; thus, it concerns questions of character. The third mode, called social ethics, recognizes that values and choices are not only expressed in individual actions, but are embodied effectively in social structures, and asks what structures are needed to support values such as justice and respect for human life and dignity View full abstract»

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Computer, the flagship publication of the IEEE Computer Society, publishes highly acclaimed peer-reviewed articles written for and by professionals representing the full spectrum of computing technology from hardware to software and from current research to new applications.

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Editor-in-Chief
Ron Vetter
University of North Carolina
Wilmington