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Computer Science Technical Reports

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Articles 181 - 210 of 772

Full-Text Articles in Computer Sciences

Exclusion And Object Tracking In A Network Of Processes, Yih-Kuen Tsay, Chien-Chung Huang Dec 2007

Exclusion And Object Tracking In A Network Of Processes, Yih-Kuen Tsay, Chien-Chung Huang

Computer Science Technical Reports

This paper concerns two fundamental problems in distributed computing---mutual exclusion and mobile object tracking. For a variant of the mutual exclusion problem where the network topology is taken into account, all existing distributed solutions make use of tokens. It turns out that these token-based solutions for mutual exclusion can also be adapted for object tracking, as the token behaves very much like a mobile object. To handle objects with replication, we go further to consider the more general $k$-exclusion problem which has not been as well studied in a network setting. A strong fairness property for $k$-exclusion requires that a …


Blacklistable Anonymous Credentials: Blocking Misbehaving Users Without Ttps (Extended Version), Patrick P. Tsang, Man Ho Au, Apu Kapadia, Sean W. Smith Sep 2007

Blacklistable Anonymous Credentials: Blocking Misbehaving Users Without Ttps (Extended Version), Patrick P. Tsang, Man Ho Au, Apu Kapadia, Sean W. Smith

Computer Science Technical Reports

Several credential systems have been proposed in which users can authenticate to services anonymously. Since anonymity can give users the license to misbehave, some variants allow the selective deanonymization (or linking) of misbehaving users upon a complaint to a trusted third party (TTP). The ability of the TTP to revoke a user's privacy at any time, however, is too strong a punishment for misbehavior. To limit the scope of deanonymization, systems such as ``e-cash'' have been proposed in which users are deanonymized under only certain types of well-defined misbehavior such as ``double spending.'' While useful in some applications, it is …


Yasir: A Low-Latency, High-Integrity Security Retrofit For Legacy Scada Systems, Patrick P. Tsang, Sean W. Smith Sep 2007

Yasir: A Low-Latency, High-Integrity Security Retrofit For Legacy Scada Systems, Patrick P. Tsang, Sean W. Smith

Computer Science Technical Reports

We construct a bump-in-the-wire (BITW) solution that retrofits security into time-critical communications over bandwidth-limited serial links between devices in Supervisory Control And Data Acquisition (SCADA) systems. Previous BITW solutions fail to provide the necessary security within timing constraints; the previous solution that does provide the necessary security is not BITW. At a comparable hardware cost, our BITW solution provides sufficient security, and yet incurs minimal end-to-end communication latency. A microcontroller prototype of our solution is under development.


Video Stabilization And Enhancement, Hany Farid, Jeffrey B. Woodward Sep 2007

Video Stabilization And Enhancement, Hany Farid, Jeffrey B. Woodward

Computer Science Technical Reports

We describe a simple and computationally efficient approach for video stabilization and enhancement. By combining multiple low-quality video frames, it is possible to extract a high-quality still image. This technique is particularly helpful in identifying people, license plates, etc. from low-quality video surveillance cameras.


Fast-Converging Tatonnement Algorithms For The Market Problem, R Cole, L Fleischer Aug 2007

Fast-Converging Tatonnement Algorithms For The Market Problem, R Cole, L Fleischer

Computer Science Technical Reports

Why might markets tend toward and remain near equilibrium prices? In an effort to shed light on this question from an algorithmic perspective, this paper defines and analyzes two simple tatonnement algorithms that differ from previous algorithms that have been subject to asymptotic analysis in three significant respects: the price update for a good depends only on the price, demand, and supply for that good, and on no other information; the price update for each good occurs distributively and asynchronously; the algorithms work (and the analyses hold) from an arbitrary starting point. Our algorithm introduces a new and natural update …


Secure Cryptographic Precomputation With Insecure Memory, Patrick P. Tsang, Sean W. Smith Jul 2007

Secure Cryptographic Precomputation With Insecure Memory, Patrick P. Tsang, Sean W. Smith

Computer Science Technical Reports

Precomputation dramatically reduces the execution latency of many cryptographic algorithms. To sustain the reduced latency over time during which these algorithms are routinely invoked, however, a pool of precomputation results must be stored and be readily available. While precomputation is an old and well-known technique, how to securely and yet efficiently store these precomputation results has largely been ignored. For instance, requiring tamper-proof memory would be too expensive, if not unrealistic, for precomputation to be cost-effective. In this paper, we propose an architecture that provides secure storage for cryptographic precomputation using only insecure memory, which may be eavesdropped or even …


Light-Based Sample Reduction Methods For Interactive Relighting Of Scenes With Minute Geometric Scale, William B. Kerr, Fabio Pellacini Jul 2007

Light-Based Sample Reduction Methods For Interactive Relighting Of Scenes With Minute Geometric Scale, William B. Kerr, Fabio Pellacini

Computer Science Technical Reports

Rendering production-quality cinematic scenes requires high computational and temporal costs. From an artist's perspective, one must wait for several hours for feedback on even minute changes of light positions and parameters. Previous work approximates scenes so that adjustments on lights may be carried out with interactive feedback, so long as geometry and materials remain constant. We build on these methods by proposing means by which objects with high geometric complexity at the subpixel level, such as hair and foliage, can be approximated for real-time cinematic relighting. Our methods make no assumptions about the geometry or shaders in a scene, and …


When One Pipeline Is Not Enough, Thomas H. Cormen, Priya Natarajan, Elena Riccio Davidson Jun 2007

When One Pipeline Is Not Enough, Thomas H. Cormen, Priya Natarajan, Elena Riccio Davidson

Computer Science Technical Reports

Pipelines that operate on buffers often work well to mitigate the high latency inherent in interprocessor communication and in accessing data on disk. Running a single pipeline on each node works well when each pipeline stage consumes and produces data at the same rate. If a stage might consume data faster or slower than it produces data, a single pipeline becomes unwieldy. We describe how we have extended the FG programming environment to support multiple pipelines in two forms. When a node might send and receive data at different rates during interprocessor communication, we use disjoint pipelines that send and …


A Combined Routing Method For Wireless Ad Hoc Networks, Soumendra Nanda, Zhenhui Jiang, David Kotz Jun 2007

A Combined Routing Method For Wireless Ad Hoc Networks, Soumendra Nanda, Zhenhui Jiang, David Kotz

Computer Science Technical Reports

To make ad hoc wireless networks adaptive to different mobility and traffic patterns, this paper proposes an approach to swap from one protocol to another protocol dynamically, while routing continues. By the insertion of a thin new layer, we were able to make each node in the ad hoc wireless network notify each other about the protocol swap. To ensure that routing works efficiently after the protocol swap, we initialized the destination routing protocol's data structures and reused the previous routing information to build the new routing table. We also tested our approach under different network topologies and traffic patterns …


Dumbots: Unexpected Botnets Through Networked Embedded Devices, Kwang-Hyun Baek, Sergey Bratus, Sara Sinclair May 2007

Dumbots: Unexpected Botnets Through Networked Embedded Devices, Kwang-Hyun Baek, Sergey Bratus, Sara Sinclair

Computer Science Technical Reports

Currently, work on botnets focuses primarily on PCs. However, as lightweight computing devices with embedded operating systems become more ubiquitous, they present a new and very disturbing target for botnet developers. In this paper, we present both an empirical demonstration on a widely deployed multimedia box, as well as an evaluation of the deeper potential of these dumbots.


The Quality Of Open Source Production: Zealots And Good Samaritans In The Case Of Wikipedia, Denise Anthony, Sean W. Smith, Tim Williamson Apr 2007

The Quality Of Open Source Production: Zealots And Good Samaritans In The Case Of Wikipedia, Denise Anthony, Sean W. Smith, Tim Williamson

Computer Science Technical Reports

New forms of production based in electronic technology, such as open-source and open-content production, convert private commodities (typically software) into essentially public goods. A number of studies find that, like in other collective goods, incentives for reputation and group identity motivate contributions to open source goods, thereby overcoming the social dilemma inherent in producing such goods. In this paper we examine how contributor motivations affect the quality of contributions to the open-content online encyclopedia Wikipedia. We find that quality is associated with contributor motivations, but in a surprisingly inconsistent way. Registered users' quality increases with more contributions, consistent with the …


Protein Design By Mining And Sampling An Undirected Graphical Model Of Evolutionary Constraints, John Thomas, Naren Ramakrishnan, Chris Bailey-Kellogg Mar 2007

Protein Design By Mining And Sampling An Undirected Graphical Model Of Evolutionary Constraints, John Thomas, Naren Ramakrishnan, Chris Bailey-Kellogg

Computer Science Technical Reports

Evolutionary pressures on proteins to maintain structure and function have constrained their sequences over time and across species. The sequence record thus contains valuable information regarding the acceptable variation and covariation of amino acids in members of a protein family. When designing new members of a protein family, with an eye toward modified or improved stability or functionality, it is incumbent upon a protein engineer to uncover such constraints and design conforming sequences. This paper develops such an approach for protein design: we first mine an undirected probabilistic graphical model of a given protein family, and then use the model …


People-Centric Urban Sensing: Security Challenges For The New Paradigm, Peter Johnson, Apu Kapadia, David Kotz, Nikos Triandopoulos Feb 2007

People-Centric Urban Sensing: Security Challenges For The New Paradigm, Peter Johnson, Apu Kapadia, David Kotz, Nikos Triandopoulos

Computer Science Technical Reports

We study the security challenges that arise in \emph{people-centric urban sensing}, a new sensor-networking paradigm that leverages humans as part of the sensing infrastructure. Most prior work on sensor networks has focused on collecting and processing ephemeral data about the environment using a static topology and an application-aware infrastructure. People-centric urban sensing, however, involves collecting, storing, processing and fusing large volumes of data related to every-day human activities. Sensing is performed in a highly dynamic and mobile environment, and supports (among other things) pervasive computing applications that are focused on enhancing the user's experience. In such a setting, where humans …


Tr-2007011: Numerical Computation Of Determinants With Additive Preconditioning, V. Y. Pan, B. Murphy, G. Qian, R. E. Rosholt, I. Taj-Eddin Jan 2007

Tr-2007011: Numerical Computation Of Determinants With Additive Preconditioning, V. Y. Pan, B. Murphy, G. Qian, R. E. Rosholt, I. Taj-Eddin

Computer Science Technical Reports

No abstract provided.


Tr-2007010: Error-Free Computations Via Floating-Point Operations, V. Y. Pan, B. Murphy, G. Qian, R. E. Rosholt Jan 2007

Tr-2007010: Error-Free Computations Via Floating-Point Operations, V. Y. Pan, B. Murphy, G. Qian, R. E. Rosholt

Computer Science Technical Reports

No abstract provided.


Tr-2007007: Independent Component Analysis: An Introduction, Rave Harpaz Jan 2007

Tr-2007007: Independent Component Analysis: An Introduction, Rave Harpaz

Computer Science Technical Reports

No abstract provided.


Tr-2007009: Computations In The Null Spaces With Additive Preprocessing, Victor Y. Pan Jan 2007

Tr-2007009: Computations In The Null Spaces With Additive Preprocessing, Victor Y. Pan

Computer Science Technical Reports

No abstract provided.


Tr-2007014: The Schur Aggregation And Extended Iterative Refinement, V. Y. Pan, B. Murphy, R. E. Rosholt Jan 2007

Tr-2007014: The Schur Aggregation And Extended Iterative Refinement, V. Y. Pan, B. Murphy, R. E. Rosholt

Computer Science Technical Reports

No abstract provided.


Tr-2007001: On Developing User Interfaces For Children In Educational Virtual Reality Environments, Lori Scarlatos, Rebecca Friedman Jan 2007

Tr-2007001: On Developing User Interfaces For Children In Educational Virtual Reality Environments, Lori Scarlatos, Rebecca Friedman

Computer Science Technical Reports

No abstract provided.


Tr-2007020: S4lp And Local Realizability, Melvin Fitting Jan 2007

Tr-2007020: S4lp And Local Realizability, Melvin Fitting

Computer Science Technical Reports

No abstract provided.


Tr-2007002: Additive Preconditioning And Aggregation In Matrix Computations, Victor Y. Pan, Brian Murphy, Rhys Eric Rosholt, Dmitriy Ivolgin, Yuqing Tang, Xiaodong Yan Jan 2007

Tr-2007002: Additive Preconditioning And Aggregation In Matrix Computations, Victor Y. Pan, Brian Murphy, Rhys Eric Rosholt, Dmitriy Ivolgin, Yuqing Tang, Xiaodong Yan

Computer Science Technical Reports

No abstract provided.


Tr-2007004: Additive Preconditioning, Eigenspaces, And The Inverse Iteration, Victor Y. Pan, Xiaodong Yan Jan 2007

Tr-2007004: Additive Preconditioning, Eigenspaces, And The Inverse Iteration, Victor Y. Pan, Xiaodong Yan

Computer Science Technical Reports

No abstract provided.


Tr-2007005: Interpreting Knowledge Into Belief In The Presence Of Negative Introspection, Evan Goris Jan 2007

Tr-2007005: Interpreting Knowledge Into Belief In The Presence Of Negative Introspection, Evan Goris

Computer Science Technical Reports

No abstract provided.


Tr-2007006: Realizing Substitution Instances Of Modal Theorems, Melvin Fitting Jan 2007

Tr-2007006: Realizing Substitution Instances Of Modal Theorems, Melvin Fitting

Computer Science Technical Reports

No abstract provided.


Tr-2007008: The Satisfiability Problem—From The Theory Of Np-Completeness To State-Of-The-Art Sat Solvers, Rave Harpaz Jan 2007

Tr-2007008: The Satisfiability Problem—From The Theory Of Np-Completeness To State-Of-The-Art Sat Solvers, Rave Harpaz

Computer Science Technical Reports

No abstract provided.


Tr-2007015: Justification Logics And Conservative Extensions, Melvin Fitting Jan 2007

Tr-2007015: Justification Logics And Conservative Extensions, Melvin Fitting

Computer Science Technical Reports

No abstract provided.


Tr-2007017: Linear Logic With Explicit Resources, Hirohiko Kushida Jan 2007

Tr-2007017: Linear Logic With Explicit Resources, Hirohiko Kushida

Computer Science Technical Reports

No abstract provided.


Tr-2007019: Justification Logic, Sergei Artemov Jan 2007

Tr-2007019: Justification Logic, Sergei Artemov

Computer Science Technical Reports

No abstract provided.


Tr-2007021: Row-Column Pivoting In Gaussian Elimination, Victor Y. Pan, Guoliang Qian, Ai-Long Zheng, Severin Ngnosse Jan 2007

Tr-2007021: Row-Column Pivoting In Gaussian Elimination, Victor Y. Pan, Guoliang Qian, Ai-Long Zheng, Severin Ngnosse

Computer Science Technical Reports

No abstract provided.


Tr-2007022: The Schur Aggregation For Linear Systems And Determinants, V. Y. Pan, B. Murphy, G. Qian, R. E. Rosholt Jan 2007

Tr-2007022: The Schur Aggregation For Linear Systems And Determinants, V. Y. Pan, B. Murphy, G. Qian, R. E. Rosholt

Computer Science Technical Reports

No abstract provided.