BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-362 ENTRY:: February 24, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Reducing Mass Degeneracy in SAR by MS by Stable Isotopic Labeling TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Bailey-Kellogg, Chris AUTHOR:: Kelley, John J. AUTHOR:: Stein, Clifford AUTHOR:: Donald, Bruce Randall DATE:: February 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-362.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-362.pdf ABSTRACT:: Mass spectrometry (MS) promises to be an invaluable tool for functional genomics, by supporting low-cost, high-throughput experiments. However, large-scale MS faces the potential problem of mass degeneracy -- indistinguishable masses for multiple biopolymer fragments (e.g. from a limited proteolytic digest). This paper studies the tasks of planning and interpreting MS experiments that use selective isotopic labeling, thereby substantially reducing potential mass degeneracy. Our algorithms support an experimental-computational protocol called Structure-Activity Relation by Mass Spectrometry (SAR by MS), for elucidating the function of protein-DNA and protein-protein complexes. SAR by MS enzymatically cleaves a crosslinked complex and analyzes the resulting mass spectrum for mass peaks of hypothesized fragments. Depending on binding mode, some cleavage sites will be shielded; the absence of anticipated peaks implicates corresponding fragments as either part of the interaction region or inaccessible due to conformational change upon binding. Thus different mass spectra provide evidence for different structure-activity relations. We address combinatorial and algorithmic questions in the areas of data analysis (constraining binding mode based on mass signature) and experiment planning (determining an isotopic labeling strategy to reduce mass degeneracy and aid data analysis). We explore the computational complexity of these problems, obtaining upper and lower bounds. We report experimental results from implementations of our algorithms. NOTE:: This report supercedes TR99-359. To appear in the 8th International Conference on Intelligent Systems for Molecular Biology, (August 20-23, 2000) La Jolla, CA (Accepted; in press). END:: ncstrl.dartmouthcs//TR2000-362 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-363 ENTRY:: March 14, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: A Formal Semantics for SPKI TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Howell, Jon AUTHOR:: Kotz, David DATE:: March 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-363.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-363.pdf ABSTRACT:: We extend the logic and semantics of authorization due to Abadi, Lampson, et al. to support restricted delegation. Our formal model provides a simple interpretation for the variety of constructs in the Simple Public Key Infrastructure (SPKI), and lends intuition about possible extensions. We discuss both extensions that our semantics supports and extensions that it cautions against. NOTE:: This TR supercedes TR1999-361. This technical report is an extended version of a paper submitted to ESORICS 2000. For more information, see the project web page. END:: ncstrl.dartmouthcs//TR2000-363 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-364 ENTRY:: March 30, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Landmarks for absolute localization TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Howell, Jon AUTHOR:: Kotay, Keith DATE:: March 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-364.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-364.pdf ABSTRACT:: For certain experiments in mobile robotics, it is convenient to eliminate positional estimation error in the interest of analyzing other parts of the experiment. We designed and implemented a simple, accurate scheme for encoding and recovering absolute position information. The encoding is a two-dimensional image printed on the plane of the floor, and the absolute position information is recovered using a downward-looking video camera mounted on a mobile robot. NOTE:: This document describes work done in the Dartmouth Robotics Laboratory in April of 1997 and August of 1999. It was previously ``published'' as a web page, but we thought it would make sense to document it more permanently. END:: ncstrl.dartmouthcs//TR2000-364 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-365 ENTRY:: April 20, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Mobile Agents: Motivations and State-of-the-Art Systems TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Gray, Robert S. AUTHOR:: Kotz, David AUTHOR:: Cybenko, George AUTHOR:: Rus, Daniela DATE:: April 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-365.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-365.pdf ABSTRACT:: A mobile agent is an executing program that can migrate, at times of its own choosing, from machine to machine in a heterogeneous network. On each machine, the agent interacts with stationary service agents and other resources to accomplish its task. In this chapter, we first make the case for mobile agents, discussing six strengths of mobile agents and the applications that benefit from these strengths. Although none of these strengths are unique to mobile agents, no competing technique shares all six. In other words, a mobile-agent system provides a single general framework in which a wide range of distributed applications can be implemented efficiently and easily. We then present a representative cross-section of current mobile-agent systems. NOTE:: This technical report will appear as a chapter in Jeffrey M. Bradshaw, editor, Handbook of Agent Technology, AAAI/MIT Press, 2000. In Press. END:: ncstrl.dartmouthcs//TR2000-365 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-366 ENTRY:: May 02, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Performance Analysis of Mobile Agents for Filtering Data Streams on Wireless Networks TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Kotz, David AUTHOR:: Jiang, Guofei AUTHOR:: Gray, Robert S. AUTHOR:: Cybenko, George AUTHOR:: Peterson, Ronald A. DATE:: May 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-366.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-366.pdf ABSTRACT:: Wireless networks are an ideal environment for mobile agents, because their mobility allows them to move across an unreliable link to reside on a wired host, next to or closer to the resources they need to use. Furthermore, client-specific data transformations can be moved across the wireless link, and run on a wired gateway server, with the goal of reducing bandwidth demands. In this paper we examine the tradeoffs faced when deciding whether to use mobile agents to support a data-filtering application, in which numerous wireless clients filter information from a large data stream arriving across the wired network. We develop an analytical model and use parameters from our own experiments to explore the model's implications. NOTE:: In August 2000 a revised version appeared in the International Workshop on Modeling and Simulation of Wireless and Mobile Systems (MSWiM 2000). In October 2000 a further revised version appeared as Dartmouth Technical Report TR2000-377, and was submitted to the journal Mobile Networks and Applications (ACM MONET). END:: ncstrl.dartmouthcs//TR2000-366 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-367 ENTRY:: May 08, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Approximation Algorithms for the Minimum Bends Traveling Salesman Problem TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Stein, Cliff AUTHOR:: Wagner, David P. DATE:: April 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-367.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-367.pdf ABSTRACT:: The problem of traversing a set of points in the order that minimizes the total distance traveled (traveling salesman problem) is one of the most famous and well-studied problems in combinatorial optimization. It has many applications, and has been a testbed for many of the must useful ideas in algorithm design and analysis. The usual metric, minimizing the total distance traveled, is an important one, but many other metrics are of interest. In this paper, we introduce the metric of minimizing the number of turns in the tour, given that the input points are in the Euclidean plane. To our knowledge this metric has not been studied previously. It is motivated by applications in robotics and in the movement of other heavy machinery: for many such devices turning is an expensive operation. We give approximation algorithms for several variants of the traveling salesman problem for which the metric is to minimize the number of turns. We call this the minimum bends traveling salesman problem. For the case of an arbitrary set of $n$ points in the Euclidean plane, we give an O(lg z)-approximation algorithm, where z is the maximum number of collinear points. In the worst case z can be as big as n, but z will often be much smaller. For the case when the lines are restricted to being either horizontal or vertical, we give a 2-approximation algorithm. If we have the further restriction that no two points are allowed to have the same x- or y-coordinate, we give an algorithm that finds a tour which makes at most two turns more than the optimal tour. Thus we have an approximation algorithm with an additive, rather than a multiplicative error bound. Beyond the additive error bound, our algorithm for this problem introduces several interesting algorithmic techniques for decomposing sets of points in the Euclidean plane that we believe to be of independent interest. NOTE:: Submitted to FOCS 2000. END:: ncstrl.dartmouthcs//TR2000-367 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-368 ENTRY:: January 28, 2008 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: A Simulation of Auroral Absorption TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Greenberg, Eric Michael DATE:: May 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-368.pdf ABSTRACT:: HF radio transmissions propagate long distances by reflecting off the ionosphere. At high latitudes radio propagation is strongly affected by the northern lights (aurora borealis), which causes ionization at low altitudes and hence the absorption of radio waves. Models of this process are still in a primitive state. A simulation of radio wave propagation was created in order to test Foppiano and Bradley's empirical model of auroral absorption. The simulation attempts to predict the net absorption of signals at a receiver by simulating a large number of transmitters, even though the exact sources of the signals are unknown. Although the simulation takes into account auroral and nonauroral absorption as well as other sources of path loss, the analysis focuses on the nighttime aurora. An intelligent search algorithm is used in order to efficiently adjust the model to best fit the data. The output of the simulation is qualitatively and quantitatively compared to signal levels observed with HF radio receivers located in northern Canada. The analysis allows us to develop alternative models of auroral absorption which account for the level of geomagnetic activity, and these are compared to the standard Foppiano and Bradley model. NOTE:: Advisor: Dan Rockmore END:: ncstrl.dartmouthcs//TR2000-368 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-369 ENTRY:: June 16, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Registration of Images with Dissimilar Contrast using a Hybrid Method Employing Correlation and Mutual Information TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Abram, Karolyn A. DATE:: June 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-369.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-369.pdf ABSTRACT:: The problem of fitting one image into another is commonly called "registration." Finding the best possible translation and rotation necessary to align two images is one approach to solving this problem. Registration is a crucial component of many remote sensing and medical image interpretation applications. Image alignment techniques aid in volumetric estimations of complicated structures and allow radiologists to accurately identify changes between sequential images. Radiologists require image alignment capabilities to correct for patient motion and/or content displacement between images. Numerous image registration techniques exist for correcting the alignment problems mentioned above. Unfortunately, most of these techniques, such as Correlation, fail to find a good alignment when dealing with images that differ in contrast. The Mutual Information method is able to align images independently of contrast, but it is computationally intensive. We explore a hybrid technique that utilizes both Correlation and Mutual Information. The Hybrid technique hopes to gain greater contrast independence than Correlation alone while achieving a lower running time than a pure Mutual Information technique. NOTE:: Undergraduate Honors Thesis Advisor: Daniel N. Rockmore END:: ncstrl.dartmouthcs//TR2000-369 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-370 ENTRY:: June 10, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: An Infrastructure for a Mobile-Agent System that Provides Personalized Services to Mobile Devices TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Chyi, Debbie O. DATE:: May 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-370.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-370.pdf ABSTRACT:: In this paper, we present the design of a mobile-agent system that provides a mobile user with a personalized information retrieval service and we describe the implementation of the infrastructure for such a system. This "Personal Agent System" gathers information from the Internet and uses context-aware mechanisms to manage the information according to a mobile user's needs and preferences. The user's schedule and location are the context indicators in this system. These indicators are critical in ensuring that users obtain only the information they want, receive information in a form that is most useful for viewing on their mobile device, and is notified of new information in a minimally intrusive manner. The system incorporates a rule-based learning system to enhance the personalization achieved by the system. NOTE:: Undergraduate Honors Thesis. Advisor: David F. Kotz END:: ncstrl.dartmouthcs//TR2000-370 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-372 ENTRY:: June 11, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Personal Radio TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Artz, John C. DATE:: June 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-372.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-372.pdf ABSTRACT:: With the development of new technologies that allow the broadcast of digital data over radio signals, there are many possibilities for improving upon the traditional radio station model for content delivery. The idea of Personal Radio is a system that tailors content to meet the needs of each individual. Using Global Positioning System (GPS) technology to play location specific content, the listening history to play content an appropriate number of times, and user feedback to learn personal preferences, the Personal Radio provides the listener with the content that is the most useful/interesting to them. This paper will examine the general design of such a system and present solutions developed in the implementation of several pieces of the design. NOTE:: Undergraduate Honors Thesis. Advisors: David Kotz and Daniela Rus END:: ncstrl.dartmouthcs//TR2000-372 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-373 ENTRY:: June 10, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Depth from Flash TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Martin, David B. DATE:: June 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-373.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-373.pdf ABSTRACT:: Digital camera technology has recently seen substantial improvements in image quality while lower prices have made it affordable to the average consumer. Camera manufacturers, however, are not taking full advantage of this new medium for image capture. By filtering the already digitized image produced by these cameras through on-board image processing algorithms we can dramatically increase the power of digital cameras. For example, according to experts in the photographic industry, most people simply take bad pictures. Classic examples of this phenomenon are photographs taken indoors with a point-and-shoot style camera using its built-in flash. The subjects of these photographs often seem to have a spotlight on them, making them look bright and washed out while the rest of the photograph is dark and indistinct. This can primarily be accounted for by a well known property of point light sources: falloff in brightness is inversely proportional to the square of the distance between the light and the object being illuminated. A technique first introduced in the field of computer vision has been shown to successfully recover information about the distance between the light source and objects in the world. We propose using this technique, which is readily implementable in hardware, to correct for a variety of poorly illuminated digital images. NOTE:: Undergraduate Honors Thesis. Advisor: Hany Farid END:: ncstrl.dartmouthcs//TR2000-373 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-375 ENTRY:: June 10, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: An Economic CPU-Time Market for D'Agents TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Cooper, Ezra E. K. AUTHOR:: Gray, Robert S. DATE:: June 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-375.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-375.pdf ABSTRACT:: A usable and efficient resource-management system has been created for use with D'Agents. The software dynamically negotiates a price rate for CPU time, using the competitive bids of mobile agents that offer currency in return for fast computation. The system allows mobile agents to plan their expenditures across many hosts while minimizing the time needed for their tasks. The ability to price CPU time opens the door for service owners to be compensated for the computation consumed by agents and provides an incentive for servers to allow anonymous agents. We discuss the theoretical background which makes a CPU market system possible and the performance of the D'Agents market system. NOTE:: Undergraduate honors thesis. Advisor: Bob Gray. END:: ncstrl.dartmouthcs//TR2000-375 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-376 ENTRY:: June 16, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: The complexity of planning with partially-observable Markov decision processes TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Mundhenk, Martin DATE:: June 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-376.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-376.pdf ABSTRACT:: This work surveys results on the complexity of planning under uncertainty. The planning model considered is the partially-observable Markov decision process. The general planning problems are, given such a process, (a) to calculate its performance under a given control policy, (b) to find an optimal or approximate optimal control policy, and (c) to decide whether a good policy exists. The complexity of this and related problems depend on a variety of factors, including the observability of the process state, the compactness of the process representation, the type of policy, or even the number of actions relative to the number of states. In most cases, the problem can be shown to be complete for some known complexity class. The skeleton of this survey are results from Littman, Goldsmith and Mundhenk (Journal of Artificial Intelligence Research 1998), Mundhenk (Mathematics of Operations Research 2000), Mundhenk, Goldsmith, Lusena and Allender (Journal of the ACM 2000), and Lusena, Goldsmith and Mundhenk (University of KY CS TR). But there are also some news. END:: ncstrl.dartmouthcs//TR2000-376 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-377 ENTRY:: October 12, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Performance Analysis of Mobile Agents for Filtering Data Streams on Wireless Networks TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Kotz, David AUTHOR:: Cybenko, George AUTHOR:: Gray, Robert S. AUTHOR:: Jiang, Guofei AUTHOR:: Peterson, Ronald A. AUTHOR:: Hofmann, Martin O. AUTHOR:: Chacon, Daria A. AUTHOR:: Whitebread, Kenneth R. AUTHOR:: Hendler, James DATE:: October 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-377.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-377.pdf ABSTRACT:: Wireless networks are an ideal environment for mobile agents, since their mobility allows them to move across an unreliable link to reside on a wired host, next to or closer to the resources that they need to use. Furthermore, client-specific data transformations can be moved across the wireless link and run on a wired gateway server, reducing bandwidth demands. In this paper we examine the tradeoffs faced when deciding whether to use mobile agents in a data-filtering application where numerous wireless clients filter information from a large data stream arriving across the wired network. We develop an analytical model and use parameters from filtering experiments conducted during a U.S. Navy Fleet Battle Experiment (FBE) to explore the model's implications. NOTE:: Updated version of TR2000-366. To appear, after revisions, in the journal Mobile Networks and Applications (ACM MONET). END:: ncstrl.dartmouthcs//TR2000-377 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-378 ENTRY:: October 19, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Naming and sharing resources across administrative boundaries (Volume I) TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Howell, Jon DATE:: May 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-378.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-378.pdf ABSTRACT:: I tackle the problem of naming and sharing resources across administrative boundaries. Conventional systems manifest the hierarchy of typical administrative structure in the structure of their own mechanism. While natural for communication that follows hierarchical patterns, such systems interfere with naming and sharing that cross administrative boundaries, and therefore cause headaches for both users and administrators. I propose to organize resource naming and security, not around administrative domains, but around the sharing patterns of users. The dissertation is organized into four main parts. First, I discuss the challenges and tradeoffs involved in naming resources and consider a variety of existing approaches to naming. Second, I consider the architectural requirements for user-centric sharing. I evaluate existing systems with respect to these requirements. Third, to support the sharing architecture, I develop a formal logic of sharing that captures the notion of restricted delegation. Restricted delegation ensures that users can use the same mechanisms to share resources consistently, regardless of the origin of the resource, or with whom the user wishes to share the resource next. A formal semantics gives unambiguous meaning to the logic. I apply the formalism to the Simple Public Key Infrastructure and discuss how the formalism either supports or discourages potential extensions to such a system. Finally, I use the formalism to drive a user-centric sharing implementation for distributed systems. I show how this implementation enables end-to-end authorization, a feature that makes heterogeneous distributed systems more secure and easier to audit. Conventionally, gateway services that bridge administrative domains, add abstraction, or translate protocols typically impede the flow of authorization information from client to server. In contrast, end-to-end authorization enables us to build gateway services that preserve authorization information, hence we reduce the size of the trusted computing base and enable more effective auditing. I demonstrate my implementation and show how it enables end-to-end authorization across various boundaries. I measure my implementation and argue that its performance tracks that of similar authorization mechanisms without end-to-end structure. I conclude that my user-centric philosophy of naming and sharing benefits both users and administrators. NOTE:: This technical report represents Volume One of the dissertation. Volume One (187 pages) is the heart of the dissertation. Volume Two (237 pages) contains a software manual introduced with illustrated code fragments, plus plots of the raw data used for the experimental results presented in Volume One. That material is optional; I recommend that the interested reader begin with just Volume One. Volume II is available as TR2000-379. Please note that a list of errata is available as TR2000-380. END:: ncstrl.dartmouthcs//TR2000-378 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-379 ENTRY:: October 19, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Naming and sharing resources across administrative boundaries (Volume II) TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Howell, Jon DATE:: May 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-379.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-379.pdf ABSTRACT:: I tackle the problem of naming and sharing resources across administrative boundaries. Conventional systems manifest the hierarchy of typical administrative structure in the structure of their own mechanism. While natural for communication that follows hierarchical patterns, such systems interfere with naming and sharing that cross administrative boundaries, and therefore cause headaches for both users and administrators. I propose to organize resource naming and security, not around administrative domains, but around the sharing patterns of users. The dissertation is organized into four main parts. First, I discuss the challenges and tradeoffs involved in naming resources and consider a variety of existing approaches to naming. Second, I consider the architectural requirements for user-centric sharing. I evaluate existing systems with respect to these requirements. Third, to support the sharing architecture, I develop a formal logic of sharing that captures the notion of restricted delegation. Restricted delegation ensures that users can use the same mechanisms to share resources consistently, regardless of the origin of the resource, or with whom the user wishes to share the resource next. A formal semantics gives unambiguous meaning to the logic. I apply the formalism to the Simple Public Key Infrastructure and discuss how the formalism either supports or discourages potential extensions to such a system. Finally, I use the formalism to drive a user-centric sharing implementation for distributed systems. I show how this implementation enables end-to-end authorization, a feature that makes heterogeneous distributed systems more secure and easier to audit. Conventionally, gateway services that bridge administrative domains, add abstraction, or translate protocols typically impede the flow of authorization information from client to server. In contrast, end-to-end authorization enables us to build gateway services that preserve authorization information, hence we reduce the size of the trusted computing base and enable more effective auditing. I demonstrate my implementation and show how it enables end-to-end authorization across various boundaries. I measure my implementation and argue that its performance tracks that of similar authorization mechanisms without end-to-end structure. I conclude that my user-centric philosophy of naming and sharing benefits both users and administrators. NOTE:: This technical report represents Volume Two of the dissertation. Volume One (187 pages) is the heart of the dissertation. Volume Two (237 pages) contains a software manual introduced with illustrated code fragments, plus plots of the raw data used for the experimental results presented in Volume One. That material is optional; I recommend that the interested reader begin with just Volume One. Volume I is available as TR2000-378. Please note that a list of errata is available as TR2000-380. END:: ncstrl.dartmouthcs//TR2000-379 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-380 ENTRY:: October 19, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Naming and sharing resources across administrative boundaries (errata) TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Howell, Jon DATE:: May 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-380.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-380.pdf ABSTRACT:: I tackle the problem of naming and sharing resources across administrative boundaries. Conventional systems manifest the hierarchy of typical administrative structure in the structure of their own mechanism. While natural for communication that follows hierarchical patterns, such systems interfere with naming and sharing that cross administrative boundaries, and therefore cause headaches for both users and administrators. I propose to organize resource naming and security, not around administrative domains, but around the sharing patterns of users. The dissertation is organized into four main parts. First, I discuss the challenges and tradeoffs involved in naming resources and consider a variety of existing approaches to naming. Second, I consider the architectural requirements for user-centric sharing. I evaluate existing systems with respect to these requirements. Third, to support the sharing architecture, I develop a formal logic of sharing that captures the notion of restricted delegation. Restricted delegation ensures that users can use the same mechanisms to share resources consistently, regardless of the origin of the resource, or with whom the user wishes to share the resource next. A formal semantics gives unambiguous meaning to the logic. I apply the formalism to the Simple Public Key Infrastructure and discuss how the formalism either supports or discourages potential extensions to such a system. Finally, I use the formalism to drive a user-centric sharing implementation for distributed systems. I show how this implementation enables end-to-end authorization, a feature that makes heterogeneous distributed systems more secure and easier to audit. Conventionally, gateway services that bridge administrative domains, add abstraction, or translate protocols typically impede the flow of authorization information from client to server. In contrast, end-to-end authorization enables us to build gateway services that preserve authorization information, hence we reduce the size of the trusted computing base and enable more effective auditing. I demonstrate my implementation and show how it enables end-to-end authorization across various boundaries. I measure my implementation and argue that its performance tracks that of similar authorization mechanisms without end-to-end structure. I conclude that my user-centric philosophy of naming and sharing benefits both users and administrators. NOTE:: This technical report contains errata for the dissertation. Volume One (187 pages) is the heart of the dissertation. Volume Two (237 pages) contains a software manual introduced with illustrated code fragments, plus plots of the raw data used for the experimental results presented in Volume One. That material is optional; I recommend that the interested reader begin with just Volume One. Volume I is available as TR2000-378. Volume II is available as TR2000-379. END:: ncstrl.dartmouthcs//TR2000-380 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-381 ENTRY:: November 21, 2000 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: A Survey of Context-Aware Mobile Computing Research TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Chen, Guanling AUTHOR:: Kotz, David DATE:: November 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-381.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-381.pdf ABSTRACT:: Context-aware computing is a mobile computing paradigm in which applications can discover and take advantage of contextual information (such as user location, time of day, nearby people and devices, and user activity). Since it was proposed about a decade ago, many researchers have studied this topic and built several context-aware applications to demonstrate the usefulness of this new technology. Context-aware applications (or the system infrastructure to support them), however, have never been widely available to everyday users. In this survey of research on context-aware systems and applications, we looked in depth at the types of context used and models of context information, at systems that support collecting and disseminating context, and at applications that adapt to the changing context. Through this survey, it is clear that context-aware research is an old but rich area for research. The difficulties and possible solutions we outline serve as guidance for researchers hoping to make context-aware computing a reality. END:: ncstrl.dartmouthcs//TR2000-381 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-382 ENTRY:: January 30, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Bayes Optimal Metasearch: A Probabilistic Model for Combining the Results of Multiple Retrieval Systems TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Aslam, Javed A. AUTHOR:: Montague, Mark DATE:: December 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-382.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-382.pdf ABSTRACT:: We introduce a new, probabilistic model for combining the outputs of an arbitrary number of query retrieval systems. By gathering simple statistics on the average performance of a given set of query retrieval systems, we construct a Bayes optimal mechanism for combining the outputs of these systems. Our construction yields a metasearch strategy whose empirical performance nearly always exceeds the performance of any of the constituent systems. Our construction is also robust in the sense that if ``good'' and ``bad'' systems are combined, the performance of the composite is still on par with, or exceeds, that of the best constituent system. Finally, our model and theory provide theoretical and empirical avenues for the improvement of this metasearch strategy. NOTE:: Preliminary version appeared in SIGIR 2000. END:: ncstrl.dartmouthcs//TR2000-382 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2000-383 ENTRY:: January 04, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Reconstructing Ancient Egyptian Tombs TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Farid, Hany DATE:: December 2000 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2000-383.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2000-383.pdf ABSTRACT:: From the pyramids of Giza to the tombs of Thebes (modern Luxor), ancient Egypt's glorious history has produced remarkable architecture. Sadly, the nearly four million yearly tourists have taken a heavy toll on many of these ancient structures. Of particular concern are many of the tombs located opposite to Luxor on the western bank of the Nile. Digital reconstruction of these tombs has the potential to help document and preserve these important historical structures. Photographing and reconstruction of these tombs poses new and unique problems that this paper begins to address. Techniques for removing image distortions, recovering 3-D shape, and correcting for lighting imbalances are discussed. A complete reconstruction of the tomb of Sennedjem is shown. END:: ncstrl.dartmouthcs//TR2000-383 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-384 ENTRY:: January 11, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Ambiguity-Directed Sampling for Qualitative Analysis of Sparse Data from Spatially-Distributed Physical Systems TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Bailey-Kellogg, Chris AUTHOR:: Ramakrishnan, Naren DATE:: January 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-384.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-384.pdf ABSTRACT:: A number of important scientific and engineering applications, such as fluid dynamics simulation and aircraft design, require analysis of spatially-distributed data from expensive experiments and complex simulations. In such data-scarce applications, it is advantageous to use models of given sparse data to identify promising regions for additional data collection. This paper presents a principled mechanism for applying domain-specific knowledge to design focused sampling strategies. In particular, our approach uses ambiguities identified in a multi-level qualitative analysis of sparse data to guide iterative data collection. Two case studies demonstrate that this approach leads to highly effective sampling decisions that are also explainable in terms of problem structures and domain knowledge. END:: ncstrl.dartmouthcs//TR2001-384 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-385 ENTRY:: January 25, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Lock-free Scheduling of Logical Processes in Parallel Simulation TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Liu, Xiaowen AUTHOR:: Nicol, David M. AUTHOR:: Tan, King DATE:: January 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-385.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-385.pdf ABSTRACT:: With fixed lookahead information in a simulation model, the overhead of asynchronous conservative parallel simulation lies in the mechanism used for propagating time updates in order for logical processes to safely advance their local simulation clocks. Studies have shown that a good scheduling algorithm should preferentially schedule processes containing events on the critical path. This paper introduces a lock-free algorithm for scheduling logical processes in conservative parallel discrete-event simulation on shared-memory multiprocessor machines. The algorithm uses fetch\&add operations that help avoid inefficiencies associated with using locks. The lock-free algorithm is robust. Experiments show that, compared with the scheduling algorithm using locks, the lock-free algorithm exhibits better performance when the number of logical processes assigned to each processor is small or when the workload becomes significant. In models with large number of logical processes, our algorithm shows only modest increase in execution time due to the overhead in the algorithm for extra bookkeeping. NOTE:: A revision of this report appears on PADS 2001. END:: ncstrl.dartmouthcs//TR2001-385 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-386 ENTRY:: January 30, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Mobile-Agent versus Client/Server Performance: Scalability in an Information-Retrieval Task TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Gray, Robert S. AUTHOR:: Kotz, David AUTHOR:: Peterson, Ronald A. AUTHOR:: Gerken, Peter AUTHOR:: Hofmann, Martin AUTHOR:: Chacon, Daria AUTHOR:: Hill, Greg AUTHOR:: Suri, Niranjan DATE:: January 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-386.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-386.pdf ABSTRACT:: Mobile agents are programs that can jump from host to host in the network, at times and to places of their own choosing. Many groups have developed mobile-agent software platforms, and several mobile-agent applications. Experiments show that mobile agents can, among other things, lead to faster applications, reduced bandwidth demands, or less dependence on a reliable network connection. There are few if any studies of the scalability of mobile-agent servers, particularly as the number of clients grows. We present some recent performance and scalability experiments that compare three mobile-agent platforms with each other and with a traditional client/server approach. The experiments show that mobile agents often outperform client/server solutions, but also demonstrate the deep interaction between environmental and application parameters. The three mobile-agent platforms have similar behavior but their absolute performance varies with underlying implementation choices. NOTE:: Revised version appeared in Mobile Agents 2001. See here. END:: ncstrl.dartmouthcs//TR2001-386 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-387 ENTRY:: March 01, 2008 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: A simple bound on the expected height of a randomly built binary search tree TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Aslam, Javed A. DATE:: Sometime 2001 ABSTRACT:: NOTE:: Abstract and paper lost. END:: ncstrl.dartmouthcs//TR2001-387 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-388 ENTRY:: May 24, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Applying the Vector Radix Method to Multidimensional, Multiprocessor, Out-of-Core Fast Fourier Transforms TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Ringenburg, Michael F. DATE:: March 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-388.ps.Z ABSTRACT:: We describe an efficient algorithm for calculating Fast Fourier Transforms on matrices of arbitrarily high dimension using the vector-radix method when the problem size is out-of-core (i.e., when the size of the data set is larger than the total available memory of the system). The algorithm takes advantage of multiple processors when they are present, but it is also efficient on single-processor systems. Our work is an extension of work done by Lauren Baptist in [Bapt99], which applied the vector-radix method to 2-dimensional out-of-core matrices. To determine the effectiveness of the algorithm, we present empirical results as well as an analysis of the I/O, communication, and computational complexity. We perform the empirical tests on a DEC 2100 server and on a cluster of Pentium-based Linux workstations. We compare our results with the traditional dimensional method of calculating multidimensional FFTs, and show that as the number of dimensions increases, the vector-radix-based algorithm becomes increasingly effective relative to the dimensional method. In order to calculate the complexity of the algorithm, it was necessary to develop a method for analyzing the interprocessor communication costs of the BMMC data-permutation algorithm (presented in [CSW98]) used by our FFT algorithms. We present this analysis method and show how it was derived. NOTE:: Masters Thesis. Advisor: Tom Cormen. END:: ncstrl.dartmouthcs//TR2001-388 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-389 ENTRY:: June 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Improving a Brokering System for Linking Distributed Simulations TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Stephens, Thomas B. DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-389.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-389.pdf ABSTRACT:: The Agent Based Environment for Linking Simulations (ABELS) is a software framework designed to provide disparate simulations with dynamically updated data sources. It allows simulations and other agents to join a "cloud" of interacting producers and consumers of data. Once they have joined the cloud, they can publish services to other members and use methods published by others. This paper presents the initial design of a set of matchmaking components for the ABELS framework. These components dictate how services describe their abilities and requirements to ABELS. Furthermore, they help ABELS successfully match data producing services to the requests of data consuming clients. We begin by describing a system for a data producing service to describe itself to the ABELS cloud, as well as a corresponding system for a data consumer to describe its needs. We then describe in detail the three components that make up the ABELS matchmaking system: the match ranker, which ranks a data producer's ability to fill the request of a data consumer; the thesaurus, which helps the match ranker recognize closely related terms; and the unit database, which allows participants in the ABELS system to translate between related data units. We also discuss how these basic components can be built upon and improved in future versions of the ABELS framework. NOTE:: Senior Honors Thesis. Advisor: Linda F. Wilson. END:: ncstrl.dartmouthcs//TR2001-389 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-390 ENTRY:: June 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Mobile Voice Over IP (MVOIP): An Application-level Protocol TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Mills-Tettey, G. Ayorkor DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-390.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-390.pdf ABSTRACT:: Current Voice over Internet Protocol (VOIP) protocols require participating hosts to have fixed IP addresses for the duration of a VOIP call. When using a wireless-enabled host, such as a tablet computer on an 802.11 wireless network, it is possible for a participant in a VOIP call to roam around the network, moving from one subnet to another and needing to change IP addresses. This address change creates the need for mobility support in VOIP applications. We present the design of Mobile Voice over IP (MVOIP), an application-level protocol that enables such mobility in a VOIP application based on the ITU H.323 protocol stack. An MVOIP application uses hints from the surrounding network to determine that it has switched subnets. It then initiates a hand-off procedure that comprises pausing its current calls, obtaining a valid IP address for the current subnet, and reconnecting to the remote party with whom it was in a call. Testing the system shows that on a Windows 2000 platform there is a perceivable delay in the hand-off process, most of which is spent in the Windows API for obtaining DHCP addresses. Despite this bottleneck, MVOIP works well on a wireless network. NOTE:: Senior Honors Thesis. Advisor: David Kotz. END:: ncstrl.dartmouthcs//TR2001-390 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-391 ENTRY:: June 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: A Directory Infrastructure to Support Mobile Services TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Khalid, Ammar DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-391.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-391.pdf ABSTRACT:: Traditional Voice-over-IP applications such as Microsoft NetMeeting assume that the user is on a machine with a fixed IP address. If, however, the user connects to the Internet, via a wireless network, on a handheld device, his IP address frequently changes as he moves from one subnet to another. In such a situation, we need a service that can be queried for the most current IP address of a person whom we wish to contact. In this project, we design and implement such a directory service. The service authenticates all callers and callees, is robust against most host failure, and scales to several thousand registered users. NOTE:: Senior Honors Thesis. Advisor: David Kotz. END:: ncstrl.dartmouthcs//TR2001-391 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-392 ENTRY:: June 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: SmartReminder: A Case Study on Context-Sensitive Applications TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Mathias, Arun DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-392.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-392.pdf ABSTRACT:: Designing context-sensitive applications is challenging. We design and implement SmartReminder to explore designing context-sensitive applications and to demonstrate how the SOLAR system can be used in developing such applications. SmartReminder is an application that reminds the user based on contextual information. Current appointment-reminder applications remind the user about their appointments at an arbitrarily specified time. For instance, they might remind the user ten minutes before each appointment. SmartReminder, on the other hand, uses contextual information, like location, to better estimate the appropriate reminder time for each appointment. It reminds the user based on where they are, where they need to be, and how long it will take them to get there. This paper presents SmartReminder as an illustration of how context-sensitive applications can be designed using the SOLAR system for dissemination of contextual information. NOTE:: Senior Honors Thesis. Advisor: David Kotz. END:: ncstrl.dartmouthcs//TR2001-392 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-393 ENTRY:: June 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Measuring early usage of Dartmouth's wireless network TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Stern, Pablo DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-393.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-393.pdf ABSTRACT:: In Spring 2001, Dartmouth College installed a campus-wide 802.11b wireless network. To understand how that network is used, we examined the usage characteristics of the network over a five-week period. We monitored access points to determine user behavior, and user and network traffic characteristics. Because our study coincided with the deployment of the access points, our analysis captures the growth of a wireless network. The results of this study help understand the behavior of mobile users and provide a reference to network engineers wishing to deploy and expand similar wireless networks. NOTE:: Senior Honors Thesis. Advisor: David Kotz. END:: ncstrl.dartmouthcs//TR2001-393 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-394 ENTRY:: June 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: An Empirical Study of Training and Testing Error in Boosting TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Latham, David D. DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-394.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-394.pdf ABSTRACT:: Bounds have been proven for both training and testing error for the boosting algorithm AdaBoost, but in practice neither seem to produce a particularly tight bound. In this paper we share some observations of these bounds from empirical results, and then explore some properties of the algorithm with an eye towards finding an improved bound for the performance of AdaBoost. Based on our empirical evidence, the error of a hypothesis which labels examples probabilistically based upon the confidence of the vote of the weak hypotheses forms a tighter bound for the training error. NOTE:: Senior Honors Thesis. Advisor: Jay Aslam. END:: ncstrl.dartmouthcs//TR2001-394 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-395 ENTRY:: June 05, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: An Implementation of Object-Oriented Program Transformation for Thought-Guided Debugging TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Wong, Tiffany M. DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-395.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-395.pdf ABSTRACT:: This paper presents our design and implementation of program transformation for C++ that will be used in the context of a thought-guided debugging system. The program uses a lexical analyzer written in Flex and a grammar written in Bison that work in conjunction to scan the inputted C++ code for function definitions and class definitions. The code is then transformed to produce trace information for each defined function, while the original functionality of the code is left untouched. We also implement two additional data structures that are used for information storage during the course of the program. NOTE:: Senior Honors Thesis. Advisor: Tom Cormen END:: ncstrl.dartmouthcs//TR2001-395 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-396 ENTRY:: June 05, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Implementing a Database Information System for an Electronic Baseball Scorecard TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Wong, Tiffany M. DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-396.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-396.pdf ABSTRACT:: We present our design and implementation of a database system of information storage and retrieval for an electronic baseball scorecard. The program uses the relational MySQL database to hold information and a Tcl API to handle interactions between the database and the user interface code. This paper discusses the inner workings of how information storage was broken down inside the database, how queries were internally constructed in accordance with the user's input, and how statistics for players and teams were calculated and returned to the user. Finally, we discuss some limitations attached to our current implementation of the program and propose improvements that can be made in future versions. NOTE:: Senior Honors Thesis. Advisor: Tom Cormen END:: ncstrl.dartmouthcs//TR2001-396 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-397 ENTRY:: June 01, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Supporting Adaptive Ubiquitous Applications with the SOLAR System TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Chen, Guanling AUTHOR:: Kotz, David DATE:: May 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-397.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-397.pdf ABSTRACT:: As we embed more computers into our daily environment, ubiquitous computing promises to make them less noticeable and help to prevent information overload. We see, however, few ubiquitous applications that are able to adapt to the dynamics of user, physical, and computational context. We believe that there are two challenges causing this lack of ubiquitous applications: there is no flexible and scalable way to support information collection and dissemination in a ubiquitous and mobile environment, and there is no general approach to building adaptive applications given heterogeneous contextual information. We propose a system infrastructure, Solar, to meet these challenges. Solar uses a subscription-based operator graph abstraction and allows dynamic composition of stackable operators to manage ubiquitous information sources. After developing a set of diverse adaptive applications, we expect to identify fundamental techniques for context-aware adaptation. Our expectation is that Solar's end-to-end support for information collection, dissemination, and utilization will make it easy to build adaptive applications for a ubiquitous mobile environment with many users and devices. END:: ncstrl.dartmouthcs//TR2001-397 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-398 ENTRY:: January 23, 2008 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: A System for Audio Personalization with Applications on Wireless Devices TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Marmaros, David DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-398.pdf ABSTRACT:: We present and analyze a system for dynamically tailoring discrete audio content for numerous users based on aggregate data and intuitive feedback mechanisms. The framework for this system utilizes a flexible client-server architecture to facilitate audio dissemination, with particular attention to distribution over wireless networks. We discuss the requirements and specifications of such a system. We further analyze the algorithms and protocols required for its operation. Finally, we outline and provide data from a demonstration of this application. NOTE:: Senior Honors Thesis. Advisors: David Kotz and Daniela Rus. END:: ncstrl.dartmouthcs//TR2001-398 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-399 ENTRY:: June 15, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: WebALPS Implementation and Performance Analysis: Using Trusted Co-servers to Enhance Privacy and Security of Web Interactions TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Jiang, Shan DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-399.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-399.pdf ABSTRACT:: The client-server model of the Web poses a fundamental trust issue: clients are forced to trust in secrecy and correctness of computation occurring at a remote server of unknown credibility. The current solution for this problem is to use a PKI (Public Key Infrastructure) system and SSL (Secure Sockets Layer) digital certificates to prove the claimed identity of a server and establish an authenticated, encrypted channel between the client and this server. However, this approach does not address the security risks posed by potential malicious server operators or any third parties who may penetrate the server sites. The WebALPS (Web Applications with Lots of Privacy and Security) approach is proposed to address these weaknesses by moving sensitive computations at server side into trusted co-servers running inside high-assurance secure coprocessors. In this report, we examine the foundations of the credibility of WebALPS co-servers. Then we will describe our work of designing and building a prototype WebALPS co-server, which is integrated into the widely-deployed, commercial-grade Apache server. We will also present the performance test results of our system which support the argument that WebALPS approach provides a systematic and practical way to address the remote trust issue. NOTE:: Master's thesis. END:: ncstrl.dartmouthcs//TR2001-399 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-400 ENTRY:: January 21, 2008 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: An Armored Data Vault TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Iliev, Alex DATE:: May 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-400.pdf ABSTRACT:: We consider the problem of secure long-term archiving of network traffic, an instance of the problem of storing data securely. We approach the problem using secure hardware, which enables the enforcement of flexible access policy. The policy cannot be circumvented by anyone, even insiders, and so we are assured that access to the data is as originally intended. The policy can be expressed as any feasible computation, as it will be checked inside the secure hardware without possibility of interference. We discuss our design of a device to perform such network data archiving and have implemented a prototpe device. We discuss other possible application areas of the design. NOTE:: Senior Honors Thesis. Advisor: Sean Smith. END:: ncstrl.dartmouthcs//TR2001-400 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-401 ENTRY:: February 10, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Outbound Authentication for Programmable Secure Coprocessors TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Smith, Sean W. DATE:: March 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-401.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-401.pdf ABSTRACT:: A programmable secure coprocessor platform can help solve many security problems in distributed computing. These solutions usually require that coprocessor applications be able to participate as full-fledged parties in distributed cryptographic protocols. Thus, to fully enable these solutions, a generic platform must not only provide programmability, maintenance, and configuration in the hostile field---it must also provide outbound authentication for the entities that result. A particular application on a particular untampered device must be able to prove who it is to a party on the other side of the Internet. To be effective, a secure outbound authentication service must closely mesh with the overall security architecture. Our initial architecture only sketched a rough design for this service, and did not complete it. This paper presents our research and development experience in refining and implementing this design, to provide PKI-based outbound authentication for the IBM 4758 Model 2 secure coprocessor platform. END:: ncstrl.dartmouthcs//TR2001-401 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-402 ENTRY:: June 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Optimizing the Dimensional Method for Performing Multidimensional, Multiprocessor, Out-of-Core FFTs TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Fineman, Jeremy T. DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-402.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-402.pdf ABSTRACT:: We present an improved version of the Dimensional Method for computing multidimensional Fast Fourier Transforms (FFTs) on a multiprocessor system when the data consist of too many records to fit into memory. Data are spread across parallel disks and processed in sections. We use the Parallel Disk Model for analysis. The simple Dimensional Method performs the 1-dimensional FFTs for each dimension in term. Between each dimension, an out-of-core permutation is used to rearrange the data to contiguous locations. The improved Dimensional Method processes multiple dimensions at a time. We show that determining an optimal sequence and groupings of dimensions is NP-complete. We then analyze the effects of two modifications to the Dimensional Method independently: processing multiple dimensions at one time, and processing single dimensions in a different order. Finally, we show a lower bound on the I/O complexity of the Dimensional Method and present an algorithm that is approximately asymptotically optimal. NOTE:: Senior Honors Thesis. Advisor: Tom Cormen. END:: ncstrl.dartmouthcs//TR2001-402 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-403 ENTRY:: June 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: EcomRISK.org : A site to classify and organize the risks of performing business on the Internet TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Marcuss, Aidan S. DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-403.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-403.pdf ABSTRACT:: As the use of the Internet and other computer networks to transact business grows, there is an ever increasing need for those taking part in those transactions to understand the risks of doing so. While there are many web sites that have created valuable databases of specific vulnerabilities for certain types of hardware and software, there is a lack of focus on attempting to analyze the interaction of businesses, their systems, computer networks, and their customers and the risks that are created by either intended or unattended interactions. EcomRISK.org is a web site that presents a clear taxonomy to classify these risks and provides other features to aid in the general discussion of e-commerce risk. The site, and the taxonomy at the center of it, creates a database of these incidents so they can be clearly searched. This paper discusses the creation of EcomRISK.org, from vision to birth. NOTE:: Senior Honors Thesis. Advisor: Fillia Makedon. END:: ncstrl.dartmouthcs//TR2001-403 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-404 ENTRY:: June 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Efficient Compression of Generic Function Dispatch Tables TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Kidd, Eric DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-404.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-404.pdf ABSTRACT:: A generic function is similar to an overloaded operator, but provides a way to select an appropriate behavior at run-time instead of compile-time. Dujardin and colleagues have proposed an algorithm for building and compressing generic function dispatch tables. We present several modifications to their algorithm, including an improvement to Pseudo-Closest-Poles and two new algorithms for compressing pole tables. The two new compression algorithms are simple and fast, and one produces smaller output than the original. NOTE:: Senior Honors Thesis. Advisor: Chris Hawblitzel. END:: ncstrl.dartmouthcs//TR2001-404 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-405 ENTRY:: June 05, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: DaSSFNet: An Extension to DaSSF for High-Performance Network Modeling TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Iyigun, Mehmet DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-405.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-405.pdf ABSTRACT:: Scalable Simulation Framework (SSF) is a discrete-event simulation framework providing a unified programming interface geared towards network simulation. Dartmouth SSF (DaSSF) is a C++ implementation of SSF, designed for simulating very large-scale multi-protocol communication networks. As of the latest release, DaSSF lacks many features present in SSF and this prevents it from achieving mainstream use. To alleviate this shortcoming we designed and implemented DaSSFNet which extends DaSSF to the levels of functionality found in SSF. In this paper, we show that DaSSFNet and SSFNet are identical in operation given the same input. We also show that DaSSFNet is about twice as fast and has one third the memory consumption of SSFNet when simulating identical networks. Therefore, we argue, that the DaSSF simulation package with DaSSFNet now offers a viable alternative to SSF in high-performance network simulation. NOTE:: Senior Honors Thesis. Advisor: David M. Nicol END:: ncstrl.dartmouthcs//TR2001-405 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-406 ENTRY:: June 07, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Fastab: Solving the Pitch to Notation Problem TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Robin, Jeremy I. DATE:: May 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-406.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-406.pdf ABSTRACT:: I have always been frustrated with the length of time necessary to notate a piece of music. Computers have simplified so many other aspects of our lives, it seems that they should be able to simplify this task as well. In fact, there are already two distinct ways that engineers have attempted to attack this problem. The first analyzes the waveform generated by microphone input and relies on Fourier Analysis and other similar methods. The other examines the analog signal generated by a electric guitar-like pickup placed beneath the strings. The method used by Fastab relies much less on the musical properties of an instrument. Instead, Fastab records where and when the fingers and pick contact the instrument using digital electronics and microprocessor technology. Fastab provides a solution to the pitch to notation problem which is cheaper and more accurate than any other device available today. NOTE:: Senior Honors Thesis. Advisor: Scot Drysdale END:: ncstrl.dartmouthcs//TR2001-406 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-407 ENTRY:: June 07, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: TCP/IP Implementation within the Dartmouth Scalable Simulation Framework TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Khankin, Michael G. DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-407.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-407.pdf ABSTRACT:: This paper discusses TCP/IP networking, and in particular, the DaSSF implementation of TCP/IP. The paper reviews the protocols, outlines the implementation design, and demonstrates some tests. In addition, some performance and memory usage analysis is performed. We find DaSSF TCP/IP to be a viable option to the existing SSF. DaSSF TCP/IP is faster and uses less memory so we can simulate larger, more complex, models. NOTE:: Senior Honors Thesis. Advisor: David M. Nicol END:: ncstrl.dartmouthcs//TR2001-407 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-408 ENTRY:: June 11, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Market-based Control of Mobile-agent Systems TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Bredin, Jonathan L. DATE:: June 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-408.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-408.pdf ABSTRACT:: Modern distributed systems scatter sensors, storage, and computation throughout the environment. Ideally these devices communicate and share resources, but there is seldom motivation for a device's owner to yield control to another user. We establish markets for computational resources to motivate principals to share resources with arbitrary users, to enforce priority in distributed systems, to provide flexible and rational limitations on the potential of an application, and to provide a lightweight structure to balance the workload over time and between devices. As proof of concept, we implement a structure software agents can use to discover and negotiate access to networked resources. The structure separates discovery, authentication, and consumption enforcement as separate orthogonal issues to give system designers flexibility. Mobile agents represent informational and computational flow. We develop mechanisms that distributively allocate computation among mobile agents in two settings. The first models a situation where users collectively own networked computing resources and require priority enforcement. We extend the allocation mechanism to allow resource reservation to mitigate utility volatility. The second, more general model relaxes the ownership assumption. We apply our computational market to an open setting where a principal's chief concern is revenue maximization. Our simulations compare the performance of market-based allocation policies to traditional policies and relate the cost of ownership and consumption separation. We observe that our markets effectively prioritize applications' performance, can operate under uncertainty and network delay, provide metrics to balance network load, and allow measurement of market-participation risk versus reservation-based computation. In addition to allocation problems, we investigate resource selection to optimize execution time. The problem is NP-complete if the costs and latencies are constant. Both metrics' dependence on the chosen set complicates matters. We study how a greedy approach, a novel heuristic, and a shortest-constrained-path strategy perform in mobile-agent applications. Market-based computational-resource allocation fertilizes applications where previously there was a dearth of motive for or means of cooperation. The rationale behind mobile-agent performance optimization is also useful for resource allocation in general distributed systems where an application has a sequence of dependent tasks or when data collection is expensive. NOTE:: A Ph.D thesis from the Department of Computer Science, Dartmouth College. END:: ncstrl.dartmouthcs//TR2001-408 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-409 ENTRY:: February 10, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Web Spoofing 2001 TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Yuan, Yougu AUTHOR:: Ye, Eileen Zishuang AUTHOR:: Smith, Sean W. DATE:: July 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-409.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-409.pdf ABSTRACT:: The Web is currently the pre-eminent medium for electronic service delivery to remote users. As a consequence, authentication of servers is more important than ever. Even sophisticated users base their decision whether or not to trust a site on browser cues---such as location bar information, SSL icons, SSL warnings, certificate information, response time, etc. In their seminal work on web spoofing, Felten et al showed how a malicious server could forge some of these cues---but using approaches that are no longer reproducible. However, subsequent evolution of Web tools has not only patched security holes---it has also added new technology to make pages more interactive and vivid. In this paper, we explore the feasibility of web spoofing using this new technology---and we show how, in many cases, every one of the above cues can be forged. In particular, we show how a malicious server can forge all the SSL information a client sees---thus providing a cautionary tale about the security of one of the most common applications of PKI. We stress that these techniques have been implemented, and are available for public demonstration. END:: ncstrl.dartmouthcs//TR2001-409 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-410 ENTRY:: February 12, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Securing Web Servers against Insider Attack TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Jiang, Shan AUTHOR:: Smith, Sean AUTHOR:: Minami, Kazuhiro DATE:: July 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-410.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-410.pdf ABSTRACT:: Too often, ``security of Web transactions'' reduces to ``encryption of the channel''---and neglects to address what happens at the server on the other end. This oversight forces clients to trust the good intentions and competence of the server operator---but gives clients no basis for that trust. Furthermore, despite academic and industrial research in secure coprocessing, many in the computer science community still regard ``secure hardware'' as a synonym for ``cryptographic accelerator.' This oversight neglects the real potential of COTS secure coprocessing technology to establish trusted islands of computation in hostile environments---such as at web servers with risk of insider attack. In this paper, we apply secure coprocessing and cryptography to solve this real problem in Web technology. We present a vision: using secure coprocessors to establish trusted co-servers at Web servers and moving sensitive computations inside these co-servers. We present a prototype implementation of this vision that scales to realistic workloads. Finally, we validate this approach by building a simple E-voting application on top of our prototype. From our experience, we conclude that this approach provides a practical and effective way to enhance the security of Web servers against insider attack. END:: ncstrl.dartmouthcs//TR2001-410 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-411 ENTRY:: July 25, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Write Once, Move Anywhere: Toward Dynamic Interoperability of Mobile Agent Systems TYPE:: Technical Report (paper) REVISION:: 3 AUTHOR:: Grimstrup, Arne AUTHOR:: Gray, Robert S. AUTHOR:: Kotz, David AUTHOR:: Cowin, Thomas AUTHOR:: Hill, Greg AUTHOR:: Suri, Niranjan AUTHOR:: Chacon, Daria AUTHOR:: Hofmann, Martin DATE:: July 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-411.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-411.pdf ABSTRACT:: Mobile agents are an increasingly popular paradigm, and in recent years there has been a proliferation of mobile-agent systems. These systems are, however, largely incompatible with each other. In particular, agents cannot migrate to a host that runs a different mobile-agent system. Prior approaches to interoperability have tried to force agents to use a common API, and so far none have succeeded. Our goal, summarized in the catch phrase ``Write Once, Move Anywhere,'' led to our efforts to develop mechanisms that support dynamic runtime interoperability of mobile-agent systems. This paper describes the Grid Mobile-Agent System, which allows agents to migrate to different mobile-agent systems. NOTE:: Revised July 25, 2001. END:: ncstrl.dartmouthcs//TR2001-411 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-412 ENTRY:: September 02, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Detecting Steganographic Messages in Digital Images TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Farid, Hany DATE:: September 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-412.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-412.pdf ABSTRACT:: Techniques and applications for information hiding have become increasingly more sophisticated and widespread. With high-resolution digital images as carriers, detecting the presence of hidden messages has also become considerably more difficult. It is sometimes possible, nevertheless, to detect (but not necessarily decipher) the presence of embedded messages. The basic approach taken here works by finding predictable higher-order statistics of ``natural'' images within a multi-scale decomposition, and then showing that embedded messages alter these statistics. END:: ncstrl.dartmouthcs//TR2001-412 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2001-413 ENTRY:: September 07, 2001 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Differential Elastic Image Registration TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Periaswamy, Senthil AUTHOR:: Farid, Hany DATE:: September 2001 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2001-413.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2001-413.pdf ABSTRACT:: We have applied techniques from differential motion estimation to the problem of automatic elastic registration of medical images. This method models the mapping between images as a locally affine but globally smooth warp. The mapping also explicitly accounts for variations in image intensities. This approach is simple and highly effective across a broad range of medical images. We show the efficacy of this approach on several synthetic and clinical images. END:: ncstrl.dartmouthcs//TR2001-413 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-414 ENTRY:: January 15, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Decentralized Control for Coordinated flow of Multi-Agent Systems TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Crespi, Valentino AUTHOR:: Cybenko, George AUTHOR:: Santini, Massimo AUTHOR:: Rus, Daniela DATE:: January 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-414.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-414.pdf ABSTRACT:: This paper describes a distributed algorithm for coordinating the flow of a mass of vehicles approaching a highway exit or a tollbooth. We provide the problem formulation, a general methodology for distributed control and an instantiation of this methodology to the coordinated flow problem. We analyze our algorithm and provide experimental data. END:: ncstrl.dartmouthcs//TR2002-414 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-415 ENTRY:: January 29, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Future Directions for Mobile-Agent Research TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Kotz, David AUTHOR:: Gray, Robert S. AUTHOR:: Rus, Daniela DATE:: January 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-415.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-415.pdf ABSTRACT:: During a discussion in September 2000 the authors examined the future of research on mobile agents and mobile code. (A mobile agent is a running program that can move from host to host in network at times and to places of its own choosing.) In this paper we summarize and reflect on that discussion. It became clear that the field should shift its emphasis toward mobile code, in all its forms, rather than to continue its narrow focus on mobile agents. Furthermore, we encourage the development of modular components, so that application designers may take advantage of code mobility without needing to rewrite their application to fit in a monolithic mobile-agent system. There are many potential applications that may productively use mobile code, but there is no ``killer application'' for mobile agents. Finally, we note that although security is an important and challenging problem, there are many applications and environments with security requirements well within the capability of existing mobile-code and mobile-agent frameworks. END:: ncstrl.dartmouthcs//TR2002-415 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-416 ENTRY:: February 04, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Virtual Hierarchies - An Architecture for Building and Maintaining Efficient and Resilient Trust Chains. TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Marchesini, John C. AUTHOR:: Smith, Sean W. DATE:: February 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-416.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-416.pdf ABSTRACT:: In Public Key Infrastructure (PKI), the simple, monopolistic CA model works fine until we consider the real world. Then, issues such as scalability and mutually suspicious organizations create the need for a multiplicity of CAs, which immediately introduces the problem of how to organize them to balance resilience to compromise against efficiency of path discovery. However, security has given us tools such as secure coprocessing, secret splitting, secret sharing, and threshold cryptography for securely carrying out computations among multiple trust domains; distributed computing has given us peer-to-peer networking, for creating self-organizing distributed systems. In this paper, we use these latter tools to address the former problem by overlaying a virtual hierarchy on a mesh architecture of peer CAs, and achieving both resilience and efficiency. END:: ncstrl.dartmouthcs//TR2002-416 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-417 ENTRY:: February 12, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Web Spoofing Revisited: SSL and Beyond TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Ye, Eileen AUTHOR:: Yuan, Yougu AUTHOR:: Smith, Sean DATE:: February 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-417.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-417.pdf ABSTRACT:: Can users believe what their browsers tell them? Even sophisticated Web users decide whether or not to trust a server based on browser cues such as location bar information, SSL icons, SSL warnings, certificate information, and response time. In their seminal work on Web spoofing, Felten et al showed how, in 1996, a malicious server could forge some of these cues. However, this work used genuine SSL sessions, and Web technology has evolved much since 1996. The Web has since become the pre-eminent medium for electronic service delivery to remote users, and the security of many commerce, government, and academic network applications critically rests on the assumption that users can authenticate the servers with which they interact. This situation raises the question: is the browser-user communication model today secure enough to warrant this assumption? In this paper, we answer this question by systematically showing how a malicious server can forge every one of the above cues. Our work extends the prior results by examining contemporary browsers, and by forging all of the SSL information a client sees, including the very existence of an SSL session (thus providing a cautionary tale about the security of one of the most common applications of PKI). We have made these techniques available for public demonstration, because anything less than working code would not convincingly answer the question. We also discuss implications and potential countermeasures, both short-term and long-term. NOTE:: This TR supercedes TR2001-409. END:: ncstrl.dartmouthcs//TR2002-417 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-418 ENTRY:: February 12, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Trusted Paths for Browsers: An Open-Source Solution to Web Spoofing TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Ye, Eileen AUTHOR:: Smith, Sean DATE:: February 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-418.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-418.pdf ABSTRACT:: The security of the vast majority of ``secure'' Web services rests on SSL server PKI. However, this PKI doesn't work if the the adversary can trick the browser into appearing to tell the user the wrong thing about the certificates and cryptography. The seminal web spoofing work of Felten et al demonstrated the potential, in 1996, for malicious servers to impersonate honest servers. Our recent follow-up work explicitly shows how malicious servers can still do this---and can also forge the existence of an SSL session and the contents of the alleged server certificate. This paper reports the results of our work to systematically defend against Web spoofing, by creating a trusted path from the browser to the user. Starting with the Mozilla source, we have implemented techniques that protect a wide variety of browser-user communications, that require little participation by the user and minimal disruption of the displayed server content. We have prepared shell scripts that install these modifications on the Mozilla source, to enable others to replicate this work. In on-going work, we are cleaning up and fine-tuning our code. In future work, we hope to examine more deeply the role of user interfaces in enabling users to make effective trust judgments. END:: ncstrl.dartmouthcs//TR2002-418 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-419 ENTRY:: August 19, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: FFTs for the 2-Sphere - Improvements and Variations TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Healy, Dennis M. AUTHOR:: Rockmore, Daniel N. AUTHOR:: Kostelec, Peter J. AUTHOR:: Moore, Sean S. B. DATE:: March 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-419.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-419.pdf ABSTRACT:: Earlier work by Driscoll and Healy has produced an efficient algorithm for computing the Fourier transform of band-limited functions on the 2-sphere. In this paper we present a reformulation and variation of the original algorithm which results in a greatly improved inverse transform, and consequent improved convolution algorithm for such functions. All require at most $O(N\log^2 N)$ operations where $N$ is the number of sample points. We also address implementation considerations and give heuristics for allowing reliable and computationally efficient floating point implementations of slightly modified algorithms. These claims are supported by extensive numerical experiments from our implementation in C on DEC, HP, SGI and Linux Pentium platforms. These results indicate that variations of the algorithm are both reliable and efficient for a large range of useful problem sizes. Performance appears to be architecture-dependent. The paper concludes with a brief discussion of a few potential applications. NOTE:: Preliminary versions of some of these results have appeared in the Dartmouth College Department of Computer Science Technical Report PCS-TR94-222 and ``An FFT for the 2-sphere and Applications'', Proc. of ICASSP-96, Volume 3, pp. 1323--1326. END:: ncstrl.dartmouthcs//TR2002-419 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-420 ENTRY:: February 28, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Context Aggregation and Dissemination in Ubiquitous Computing Systems TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Chen, Guanling AUTHOR:: Kotz, David DATE:: February 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-420.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-420.pdf ABSTRACT:: Many ``ubiquitous computing'' applications need a constant flow of information about their environment to be able to adapt to their changing context. To support these ``context-aware'' applications we propose a graph-based abstraction for collecting, aggregating, and disseminating context information. The abstraction models context information as events, produced by sources and flowing through a directed acyclic graph of event-processing operators and delivered to subscribing applications. Applications describe their desired event stream as a tree of operators that aggregate low-level context information published by existing sources into the high-level context information needed by the application. The operator graph is thus the dynamic combination of all applications' subscription trees. In this paper, we motivate and describe our graph abstraction, and discuss a variety of critical design issues. We also sketch our Solar system, an implementation that represents one point in the design space for our graph abstraction. NOTE:: To appear in WMCSA 2002. END:: ncstrl.dartmouthcs//TR2002-420 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-421 ENTRY:: February 28, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Solar: A pervasive-computing infrastructure for context-aware mobile applications TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Chen, Guanling AUTHOR:: Kotz, David DATE:: February 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-421.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-421.pdf ABSTRACT:: Emerging pervasive computing technologies transform the way we live and work by embedding computation in our surrounding environment. To avoid increasing complexity, and allow the user to concentrate on her tasks, applications must automatically adapt to their changing \emph{context}, the physical and computational environment in which they run. To support these ``context-aware'' applications we propose a graph-based abstraction for collecting, aggregating, and disseminating context information. The abstraction models context information as \emph{events}, which are produced by \emph{sources}, flow through a directed acyclic graph of event-processing \emph{operators}, and are delivered to subscribing applications. Applications describe their desired event stream as a tree of operators that aggregate low-level context information published by existing sources into the high-level context information needed by the application. The \emph{operator graph\/} is thus the dynamic combination of all applications' subscription trees. In this paper, we motivate our graph abstraction by discussing several applications under development, sketch the architecture of our system (``Solar'') that implements our abstraction, report some early experimental results from the prototype, and outline issues for future research. END:: ncstrl.dartmouthcs//TR2002-421 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-422 ENTRY:: February 28, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Controlling access to pervasive information in the ``Solar'' system TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Minami, Kazuhiro AUTHOR:: Kotz, David DATE:: February 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-422.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-422.pdf ABSTRACT:: Pervasive-computing infrastructures necessarily collect a lot of context information to disseminate to their context-aware applications. Due to the personal or proprietary nature of much of this context information, however, the infrastructure must limit access to context information to authorized persons. In this paper we propose a new access-control mechanism for event-based context-distribution infrastructures. The core of our approach is based on a conservative information-flow model of access control, but users may express discretionary relaxation of the resulting access-control list (ACL) by specifying relaxation functions. This combination of automatic ACL derivation and user-specified ACL relaxation allows access control to be determined and enforced in a decentralized, distributed system with no central administrator or central policy maker. It also allows users to express their personal balance between functionality and privacy. Finally, our infrastructure allows access-control policies to depend on context-sensitive roles, allowing great flexibility. We describe our approach in terms of a specific context-dissemination framework, the Solar system, although the same principles would apply to systems with similar properties. END:: ncstrl.dartmouthcs//TR2002-422 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-423 ENTRY:: June 17, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Characterizing Usage of a Campus-wide Wireless Network TYPE:: Technical Report (paper) REVISION:: 3 AUTHOR:: Kotz, David AUTHOR:: Essien, Kobby DATE:: March 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-423.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-423.pdf ABSTRACT:: Wireless local-area networks (WLANs) are increasingly common, but little is known about how they are used. A clear understanding of usage patterns in real WLANs is critical information to those who develop, deploy, and manage WLAN technology, as well as those who develop systems and application software for wireless networks. This paper presents results from the largest and most comprehensive trace of network activity in a large, production wireless LAN. For eleven weeks we traced the activity of nearly two thousand users drawn from a general campus population, using a campus-wide network of 476 access points spread over 161 buildings. Our study expands on those done by Tang and Baker, with a significantly larger and broader population. We found that residential traffic dominated all other traffic, particularly in residences populated by newer students; students are increasingly choosing a wireless laptop as their primary computer. Although web protocols were the single largest component of traffic volume, network backup and file sharing contributed an unexpectedly large amount to the traffic. Although there was some roaming within a network session, we were surprised by the number of situations in which cards roamed excessively, unable to settle on one access point. Cross-subnet roams were an especial problem, because they broke IP connections, indicating the need for solutions that avoid or accommodate such roams. NOTE:: A major revision of this paper appeared in Mobicom 2002. The Mobicom paper contained two erroneous figures, however; another report, TR2002-432, is the final corrected version. END:: ncstrl.dartmouthcs//TR2002-423 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-424 ENTRY:: May 16, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Metasearch: Data Fusion for Document Retrieval TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Montague, Mark H. DATE:: May 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-424.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-424.pdf ABSTRACT:: The metasearch problem is to optimally merge the ranked lists output by an arbitrary number of search systems into one ranked list. In this work: (1) We show that metasearch improves upon not just the raw performance of the input search engines, but also upon the consistency of the input search engines from query to query. (2) We experimentally prove that simply weighting input systems by their average performance can dramatically improve fusion results. (3) We show that score normalization is an important component of a metasearch engine, and that dependence upon statistical outliers appears to be the problem with the standard technique. (4) We propose a Bayesian model for metasearch that outperforms the best input system on average and has performance competetive with standard techniques. (5) We introduce the use of Social Choice Theory to the metasearch problem, modeling metasearch as a democratic election. We adapt a positional voting algorithm, the Borda Count, to create a metasearch algorithm, acheiving reasonable performance. (6) We propose a metasearch model adapted from a majoritarian voting procedure, the Condorcet algorithm. The resulting algorithm is the best performing algorithm in a number of situations. (7) We propose three upper bounds for the problem, each bounding a different class of algorithms. We present experimental results for each algorithm using two types of experiments on each of four data sets. NOTE:: Ph.D dissertation. END:: ncstrl.dartmouthcs//TR2002-424 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-425 ENTRY:: July 26, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: The Future of Cryptography Under Quantum Computers TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Barreno, Marco A. DATE:: July 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-425.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-425.pdf ABSTRACT:: Cryptography is an ancient art that has passed through many paradigms, from simple letter substitutions to polyalphabetic substitutions to rotor machines to digital encryption to public-key cryptosystems. With the possible advent of quantum computers and the strange behaviors they exhibit, a new paradigm shift in cryptography may be on the horizon. Quantum computers could hold the potential to render most modern encryption useless against a quantum-enabled adversary. The aim of this thesis is to characterize this convergence of cryptography and quantum computation. We provide definitions for cryptographic primitives that frame them in general terms with respect to complexity. We explore the various possible relationships between BQP, the primary quantum complexity class, and more familiar classes, and we analyze the possible implications for cryptography. NOTE:: This paper was written as a senior honors thesis with advisor Sean W. Smith. END:: ncstrl.dartmouthcs//TR2002-425 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-426 ENTRY:: May 30, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Role Definition Language (RDL): A Language to Describe Context-Aware Roles TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Masone, Christopher P. DATE:: May 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-426.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-426.pdf ABSTRACT:: As wireless networks become more prevalent, a widening array of computational resources becomes available to the mobile user. Since not all users should have unrestricted access to these resources, a method of access control must be devised. In a context-aware environment, context information can be used to supplement more conventional password-based access control systems. We believe the best way to achieve this is through the use of Context-Aware Role-Based Access Control, a model in which permissions are assigned to entities called roles, each principal is a member of one or more roles, and a role's membership is determined using context information. We designed and implemented RDL (Role-Definition Language), a simple, expressive and somewhat extensible programming language to facilitate the description of roles in terms of context information. NOTE:: Senior Honors Thesis. Advisor: David Kotz. END:: ncstrl.dartmouthcs//TR2002-426 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-427 ENTRY:: May 30, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Performance and Interoperability In Solar TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: White, A. Abram DATE:: June 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-427.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-427.pdf ABSTRACT:: Ubiquitous computing promises to integrate computers into our physical environment, surrounding us with applications that are able to adapt to our dynamics. Solar is a software infrastructure designed to deliver contextual information to these applications. To serve the large number and wide variety of context-aware devices envisioned by ubiquitous computing, Solar must exhibit both high performance and the ability to interoperate with many computing platforms. We created a testing framework to measure the performance of distributed systems such as Solar, as well as a pluggable data-transfer mechanism to support the dissemination of information to heterogeneous applications. This paper explores the testing framework developed, analyzes its findings concerning the performance of the current Solar prototype, presents several optimizations to Solar and their effects, and finally discusses the design of the pluggable data-transfer mechanism. NOTE:: Senior Honors Thesis. Advisor: David Kotz. See also TR2002-429. END:: ncstrl.dartmouthcs//TR2002-427 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-428 ENTRY:: June 12, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Information-theoretic Bounds on the Training and Testing Error of Boosting TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Lahaie, Sebastien M. DATE:: May 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-428.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-428.pdf ABSTRACT:: Boosting is a means of using weak learners as subroutines to produce a strong learner with markedly better accuracy. Recent results showing the connection between logistic regression and boosting provide the foundation for an information-theoretic analysis of boosting. We describe the analogy between boosting and gambling, which allows us to derive a new upper bound on training error. This upper bound explicitly describes the effect of noisy data on training error. We also use information-theoretic techniques to derive an alternative upper-bound on testing error which is independent of the size of the weak-learner space. END:: ncstrl.dartmouthcs//TR2002-428 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-429 ENTRY:: May 30, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: XSLT and XQuery as Operator Languages TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: White, A. Abram DATE:: June 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-429.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-429.pdf ABSTRACT:: Ubiquitous computing promises to integrate computers into our physical environment, surrounding us with applications that are able to adapt to our dynamics. Solar is a software infrastructure designed to deliver contextual information to these applications. Solar represents context data as events, and uses small programs called operators to filter, merge, aggregate, or transform event streams. This paper explores the possibility of using XSLT and XQuery to build language-neutral Solar operators. NOTE:: See also TR2002-427. END:: ncstrl.dartmouthcs//TR2002-429 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-430 ENTRY:: June 13, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Building Trusted Paths for Web Browsers TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Ye, Eileen Zishuang DATE:: May 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-430.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-430.pdf ABSTRACT:: The communication between the Web browser and the human user is one component of the server-client channel. It is not the user but the browser that receives all server information and establishes the secure connection. The browser's user interface signals, such as SSL lock, https protocol header et al., indicate whether the browser-server communication at the current moment is secure. Those user interface signals indicating the security status of browser should be clearly and correctly understood by the user. A survey of modern Web browsers shows the information provided by current browsers is insufficient for users to make trust judgment. Our Web spoofing work further proved that the browser status information is not reliable either. We discuss the criteria for and how to build the trusted paths between a browser and a human user. We present an open source implementation of one of the designs--synchronized random dynamic (SRD) boundary, based on Modified Mozilla source code, together with its usability study results. END:: ncstrl.dartmouthcs//TR2002-430 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-431 ENTRY:: May 30, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Analysis of Protein Sequences Using Time Frequency and Kolmogorov-Smirnov Methods TYPE:: Technical Report (paper) REVISION:: 3 AUTHOR:: Essien, Kobby RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-431.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-431.pdf DATE:: May 2002 ABSTRACT:: The plethora of genomic data currently available has resulted in a search for new algorithms and analysis techniques to interpret genomic data. In this two-fold study we explore techniques for locating critical amino acid residues in protein sequences and for estimating the similarity between proteins. We demonstrate the use of the Short-Time Fourier Transform and the Continuous Wavelet Transform together with amino acid hydrophobicity in locating important amino acid domains in proteins and also show that the Kolmogorov-Smirnov statistic can be used as a metric of protein similarity. NOTE:: Senior Honors Thesis. Advisor: Metin Akay.
END:: ncstrl.dartmouthcs//TR2002-431 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-432 ENTRY:: September 25, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Analysis of a Campus-wide Wireless Network TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Kotz, David AUTHOR:: Essien, Kobby DATE:: September 2002 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: Compressed Postscript at http://www.cs.dartmouth.edu/reports/TR2002-432.ps.Z RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2002-432.pdf ABSTRACT:: Understanding usage patterns in wireless local-area networks (WLANs) is critical for those who develop, deploy, and manage WLAN technology, as well as those who develop systems and application software for wireless networks. This paper presents results from the largest and most comprehensive trace of network activity in a large, production wireless LAN. For eleven weeks we traced the activity of nearly two thousand users drawn from a general campus population, using a campus-wide network of 476 access points spread over 161 buildings. Our study expands on those done by Tang and Baker, with a significantly larger and broader population. We found that residential traffic dominated all other traffic, particularly in residences populated by newer students; students are increasingly choosing a wireless laptop as their primary computer. Although web protocols were the single largest component of traffic volume, network backup and file sharing contributed an unexpectedly large amount to the traffic. Although there was some roaming within a network session, we were surprised by the number of situations in which cards roamed excessively, unable to settle on one access point. Cross-subnet roams were an especial problem, because they broke IP connections, indicating the need for solutions that avoid or accommodate such roams. NOTE:: This paper is a revision of the MOBICOM '02 paper by the same title. The only difference is the correction of Figures 27-28 and the associated text. This report supplants TR2002-423. END:: ncstrl.dartmouthcs//TR2002-432 BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2002-433 ENTRY:: September 27, 2002 ORGANIZATION:: Dartmouth College, Computer Science TITLE:: Using the Emulab network testbed to evaluate the Armada I/O framework for computational grids TYPE:: Technical Report (paper) R