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    Who are the best spreaders of information in a social network? The answer may surprise you.
    8 years ago by @gwpl
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    Non-repudiation is a system whereby sensitive data sent over the Internet is digitally signed at the source with a signature that can be traced to the user's computer as a safeguard against fraud, but Len Sassaman of the Catholic University of Leuven warns that making this system the default setting for all traffic on a network would enable authorities to trace the source of any online activity and take away users' anonymity. Worse still, Sassaman and University of Ireland colleague Meredith Patterson say that the One Laptop per Child (OLPC) foundation is unintentionally engaged in establishing such a system throughout the Third World by supplying inexperienced users Internet-ready laptops. Theft of the laptops is discouraged with a security model called Bitfrost in which each laptop automatically phones an anti-theft server and sends its serial number once a day so that it can get an activation key, and any machine reported stolen is refused activation. Sassaman and Patterson caution that the security model's use of non-repudiable digital signatures could be exploited by oppressive regimes to identify and silence dissidents. "They may not intend for the signatures to be used for non-repudiation, but it's possible to use them for this purpose," Sassaman says. Although the OLPC laptops are primarily intended to be used for educational purposes, which some people claim would preclude government monitoring, Sassaman says it is unlikely that the systems will be used solely by children, and that conditions in some developing nations might actually encourage children to act as whistleblowers. Sassaman and Patterson are modifying the Bitfrost security model to enable the laptops to identify each other without compromising their users' privacy, based on existing cryptographic methods that cannot be employed for non-repudiation.
    10 years ago by @gwpl
     
      acm_technews
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      University of California, Berkeley professor of electrical engineering and computer sciences Richard Karp has been named a laureate of the 2008 Kyoto Prize, Japan's equivalent of the Nobel Prize, awarded by the Inamori Foundation. Karp is being recognized for his lifetime achievements in computer theory. A senior research scientist at the International Computer Science Institute in Berkeley, he is considered one of the world's leading computer theorists. Karp's work has significantly advanced the theory of NP-completeness, conceived in 1971 by former UC Berkeley math professor Stephen Cook. Karp developed a standard method for characterizing combinatorial problems into classes and identifying their level of intractability. Combinatorial problems that are NP-complete are the most difficult to solve. "Karp's theory streamlined algorithm design for problem-solving, accelerated algorithm engineering, and brought computational complexity within the scope of scientific research," says the Inamori Foundation. NP-completeness theory has become a cornerstone in modern theoretical computer science, and in the 1980s Cook and Karp received an ACM A.M. Turing Award for their contributions to the concept of NP-completeness. Karp has recently focused on bioinformatics and computational biology, including the development of algorithms for constructing various kinds of physical maps of DNA targets, and methods for classifying biological samples on the basis of gene expression data.
      10 years ago by @gwpl
       
        acm_technews
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        Now that IBM's RoadRunner supercomputer has broken the petaflop barrier, reaching more than one thousand trillion sustained floating-point operations per second, supercomputer developers say the next step is an exascale system capable of a million trillion calculations per second, a thousand times faster than a petaflop. At the upcoming International Supercomputing Conference in Dresden, Germany, University of Tennessee professor Jack Dongarra will give a presentation on exaflop systems in the year 2019. Dongarra says performance gains are following a predictable path, with the first gigaflop system being built 22 years ago. Dongarra says there will be exaflop computing in 11 years, and that by then every system on the Top500 computing list will be at least a petaflop. He says the greatest achievement with the RoadRunner system is the programming that allows the system to utilize different processor technologies. To achieve exascale systems, Dongarra says developers will have to create new programming languages and algorithms that can calculate at high degrees of concurrency to complete calculations quickly. The difficulty in reaching that level of programming, and changing to new methods, could be the roadblock that prevents exaflop computing from being realized in a similar timeline, he says.
        10 years ago by @gwpl
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