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Articles 541 - 570 of 1104
Full-Text Articles in Computer Sciences
Twokind Authentication: Protecting Private Information In Untrustworthy Environments (Extended Version), Katelin Bailey, Apu Kapadia, Linden Vongsathorn, Sean W. Smith
Twokind Authentication: Protecting Private Information In Untrustworthy Environments (Extended Version), Katelin Bailey, Apu Kapadia, Linden Vongsathorn, Sean W. Smith
Computer Science Technical Reports
We propose and evaluate TwoKind Authentication, a simple and effective technique that allows users to limit access to their private information in untrustworthy environments. Users often log in to Internet sites from insecure computers, and more recently have started divulging their email passwords to social-networking sites, thereby putting their private communications at risk. To mitigate this problem, we explore the use of multiple authenticators for the same account that are associated with specific sets of privileges. In its simplest form, TwoKind features two modes of authentication, a low and a high authenticator. By using a low authenticator, users can signal …
Attribute-Based, Usefully Secure Email, Christopher P. Masone
Attribute-Based, Usefully Secure Email, Christopher P. Masone
Dartmouth College Ph.D Dissertations
A secure system that cannot be used by real users to secure real-world processes is not really secure at all. While many believe that usability and security are diametrically opposed, a growing body of research from the field of Human-Computer Interaction and Security (HCISEC) refutes this assumption. All researchers in this field agree that focusing on aligning usability and security goals can enable the design of systems that will be more secure under actual usage. We bring to bear tools from the social sciences (economics, sociology, psychology, etc.) not only to help us better understand why deployed systems fail, but …
Workshop Report — Crawdad Workshop 2007, Jihwang Yeo, David Kotz, Tristan Henderson
Workshop Report — Crawdad Workshop 2007, Jihwang Yeo, David Kotz, Tristan Henderson
Dartmouth Scholarship
Wireless network researchers are hungry for data about how real users, applications, and devices use real networks under real network conditions. CRAWDAD, the Community Resource for Archiving Wireless Data at Dartmouth, is an NSF-funded project that is building a wireless network data archive for the research community. We host wireless data, and provide tools and documents to make it easy to collect and use wireless network data. We hope that this resource will help researchers to identify and evaluate real and interesting problems in mobile and pervasive computing. This report outlines the CRAWDAD project and summarizes the third CRAWDAD workshop, …
Event Dissemination Via Group-Aware Stream Filtering, Ming Li, David Kotz
Event Dissemination Via Group-Aware Stream Filtering, Ming Li, David Kotz
Dartmouth Scholarship
We consider a distributed system that disseminates high-volume event streams to many simultaneous monitoring applications over a low-bandwidth network. For bandwidth efficiency, we propose a group-aware stream filtering approach, used together with multicasting, that exploits two overlooked, yet important, properties of monitoring applications: 1) many of them can tolerate some degree of “slack” in their data quality requirements, and 2) there may exist multiple subsets of the source data satisfying the quality needs of an application. We can thus choose the “best alternative” subset for each application to maximize the data overlap within the group to best benefit from multicasting. …
Linkability In Activity Inference Data Sets, Jeffrey Fielding
Linkability In Activity Inference Data Sets, Jeffrey Fielding
Dartmouth College Undergraduate Theses
Activity inference is an active area of ubiquitous computing research. By training machine learning algorithms on data from sensors worn by volunteers, researchers hope to develop software that can interact more naturally with the user by inferring what the user is doing. In this thesis, we use the same sensor data to infer which volunteer is carrying the sensors. Such inference could be useful -- for example, a mobile device might infer who is carrying it and adapt to that user's preferences. It also raises some privacy concerns, since an attacker could learn more about a user by linking together …
Making Rbac Work In Dynamic, Fast-Changing Corporate Environments, Ruslan Y. Dimov
Making Rbac Work In Dynamic, Fast-Changing Corporate Environments, Ruslan Y. Dimov
Dartmouth College Undergraduate Theses
In large organizations with tens of thousands of employees, managing individual people's permissions is tedious and error prone, and thus a possible source of security risks. Role-Based Access Control addresses this problem by grouping users into roles, which reflect job functions in the corporation. Permissions are assigned to roles instead of directly to users, which means that all users assigned to a role have the same set of permissions with respect to that role. However, adoption of RBAC in organizations such as investment banks is hindered by two main factors: first, it is costly and time-consuming to define roles. Second, …
Key Management For Secure Power Scada, Manya K. Sleeper
Key Management For Secure Power Scada, Manya K. Sleeper
Dartmouth College Undergraduate Theses
This thesis proposes a key management protocol for secure power SCADA systems that seeks to take advantage of the full security capacity of a given network by allowing devices to use public key cryptography for key management if they are capable of doing so and reverting to symmetric key cryptography only when such use is necessitated by the weakness of a given device. Allowing devices to obtain different levels of security permits SCADA networks to maximize their security in the decades before such networks are capable of implementing fully public key-based key management protocols. Such a system is obtained through …
Poster Abstract: Reliable People-Centric Sensing With Unreliable Voluntary Carriers, Cory Cornelius, Apu Kapadia, David Kotz, Dan Peebles, Minho Shin, Patrick Tsang
Poster Abstract: Reliable People-Centric Sensing With Unreliable Voluntary Carriers, Cory Cornelius, Apu Kapadia, David Kotz, Dan Peebles, Minho Shin, Patrick Tsang
Dartmouth Scholarship
As sensor technology becomes increasingly easy to integrate into personal devices such as mobile phones, clothing, and athletic equipment, there will be new applications involving opportunistic, people-centric sensing. These applications, which gather information about human activities and personal social context, raise many security and privacy challenges. In particular, data integrity is important for many applications, whether using traffic data for city planning or medical data for diagnosis. Although our AnonySense system (presented at MobiSys) addresses privacy in people-centric sensing, protecting data integrity in people-centric sensing still remains a challenge. Some mechanisms to protect privacy provide anonymity, and thus provide limited …
A Dynamically Refocusable Sampling Infrastructure For 802.11 Networks, Udayan Deshpande
A Dynamically Refocusable Sampling Infrastructure For 802.11 Networks, Udayan Deshpande
Dartmouth College Ph.D Dissertations
The edge of the Internet is increasingly wireless. Enterprises large and small, homeowners, and even whole cities have deployed Wi-Fi networks for their users, and many users never need to--- or never bother to--- use the wired network. With the advent of high-throughput wireless networks (such as 802.11n) some new construction, even of large enterprise build- ings, may no longer be wired for Ethernet. To understand Internet traffic, then, we need to understand the wireless edge. Measuring Wi-Fi traffic, however, is challenging. It is insufficient to capture traffic in the access points, or upstream of the access points, because the …
Anonysense: Opportunistic And Privacy-Preserving Context Collection, Apu Kapadia, Nikos Triandopoulos, Cory Cornelius, Dan Peebles, David Kotz
Anonysense: Opportunistic And Privacy-Preserving Context Collection, Apu Kapadia, Nikos Triandopoulos, Cory Cornelius, Dan Peebles, David Kotz
Dartmouth Scholarship
Opportunistic sensing allows applications to “task” mobile devices to measure context in a target region. For example, one could leverage sensor-equipped vehicles to measure traffic or pollution levels on a particular street, or users' mobile phones to locate (Bluetooth-enabled) objects in their neighborhood. In most proposed applications, context reports include the time and location of the event, putting the privacy of users at increased risk—even if a report has been anonymized, the accompanying time and location can reveal sufficient information to deanonymize the user whose device sent the report. \par We propose AnonySense, a general-purpose architecture for leveraging users' mobile …
Anchor-Free Localization In Mixed Wireless Sensor Network Systems, Yurong Xu
Anchor-Free Localization In Mixed Wireless Sensor Network Systems, Yurong Xu
Dartmouth College Ph.D Dissertations
Recent technological advances have fostered the emergence of Wireless Sensor Networks (WSNs), which consist of tiny, wireless, battery-powered nodes that are expected to revolutionize the ways in which we understand and construct complex physical systems. A fundamental property needed to use and maintain these WSNs is ``localization'', which allows the establishment of spatial relationships among nodes over time. This dissertation presents a series of Geographic Distributed Localization (GDL) algorithms for mixed WSNs, in which both static and mobile nodes can coexist. The GDL algorithms provide a series of useful methods for localization in mixed WSNs. First, GDL provides an approximation …
Mesh-Mon: A Monitoring And Management System For Wireless Mesh Networks, Soumendra Nanda
Mesh-Mon: A Monitoring And Management System For Wireless Mesh Networks, Soumendra Nanda
Dartmouth College Ph.D Dissertations
A mesh network is a network of wireless routers that employ multi-hop routing and can be used to provide network access for mobile clients. Mobile mesh networks can be deployed rapidly to provide an alternate communication infrastructure for emergency response operations in areas with limited or damaged infrastructure. In this dissertation, we present Dart-Mesh: a Linux-based layer-3 dual-radio two-tiered mesh network that provides complete 802.11b coverage in the Sudikoff Lab for Computer Science at Dartmouth College. We faced several challenges in building, testing, monitoring and managing this network. These challenges motivated us to design and implement Mesh-Mon, a network monitoring …
Group-Aware Stream Filtering, Ming Li
Group-Aware Stream Filtering, Ming Li
Dartmouth College Ph.D Dissertations
Recent years have witnessed a new class of monitoring applications that need to continuously collect information from remote data sources. Those data sources, such as web click-streams, stock quotes, and sensor data, are often characterized as fast-rate high-volume ``streams''. Distributed stream-processing systems are thus designed to efficiently use system resources to serve the data-acquisition needs of the applications. Most of the state-of-the-art stream-processing systems assume an Ethernet-based network whose bandwidth is abundant, and focus on mechanisms to save computational power and memory. For applications involving wireless networks, particularly multi-hop mesh networks, we recognize that the most limiting factor in efficiently …
Yasir: A Low-Latency, High-Integrity Security Retrofit For Legacy Scada Systems (Extended Version), Patrick P. Tsang, Sean W. Smith
Yasir: A Low-Latency, High-Integrity Security Retrofit For Legacy Scada Systems (Extended Version), 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 legacy Supervisory Control And Data Acquisition (SCADA) systems, on which the proper operations of critical infrastructures such as the electric power grid rely. Previous BITW solutions do not provide the necessary security within timing constraints; the previous solution that does is not BITW. At a hardware cost comparable to existing solutions, our BITW solution provides sufficient security, and yet incurs minimal end-to-end communication latency.
The Weakest Failure Detector To Solve Mutual Exclusion, Vibhor Bhatt, Nicholas Christman, Prasad Jayanti
The Weakest Failure Detector To Solve Mutual Exclusion, Vibhor Bhatt, Nicholas Christman, Prasad Jayanti
Computer Science Technical Reports
Mutual exclusion is not solvable in an asynchronous message-passing system where processes are subject to crash failures. Delporte-Gallet et. al. determined the weakest failure detector to solve this problem when a majority of processes are correct. Here we identify the weakest failure detector to solve mutual exclusion in any environment, i.e., regardless of the number of faulty processes. We also show a relation between mutual exclusion and consensus, arguably the two most fundamental problems in distributed computing. Specifically, we show that a failure detector that solves mutual exclusion is sufficient to solve non-uniform consensus but not necessarily uniform consensus.
Ppaa: Peer-To-Peer Anonymous Authentication (Extended Version), Patrick P. Tsang, Sean W. Smith
Ppaa: Peer-To-Peer Anonymous Authentication (Extended Version), Patrick P. Tsang, Sean W. Smith
Computer Science Technical Reports
In the pursuit of authentication schemes that balance user privacy and accountability, numerous anonymous credential systems have been constructed. However, existing systems assume a client-server architecture in which only the clients, but not the servers, care about their privacy. In peer-to-peer (P2P) systems where both clients and servers are peer users with privacy concerns, no existing system correctly strikes that balance between privacy and accountability. In this paper, we provide this missing piece: a credential system in which peers are {\em pseudonymous} to one another (that is, two who interact more than once can recognize each other via pseudonyms) but …
Bounded Unpopularity Matchings, Chien-Chung Huang, Telikepalli Kavitha, Dimitrios Michail, Meghana Nasre
Bounded Unpopularity Matchings, Chien-Chung Huang, Telikepalli Kavitha, Dimitrios Michail, Meghana Nasre
Computer Science Technical Reports
We investigate the following problem: given a set of jobs and a set of people with preferences over the jobs, what is the optimal way of matching people to jobs? Here we consider the notion of \emph{popularity}. A matching $M$ is popular if there is no matching $M'$ such that more people prefer $M'$ to $M$ than the other way around. Determining whether a given instance admits a popular matching and, if so, finding one, was studied in \cite{AIKM05}. If there is no popular matching, a reasonable substitute is a matching whose {\em unpopularity} is bounded. We consider two measures …
Detecting 802.11 Mac Layer Spoofing Using Received Signal Strength, Yong Sheng, Keren Tan, Guanling Chen, David Kotz, Andrew T. Campbell
Detecting 802.11 Mac Layer Spoofing Using Received Signal Strength, Yong Sheng, Keren Tan, Guanling Chen, David Kotz, Andrew T. Campbell
Dartmouth Scholarship
MAC addresses can be easily spoofed in 802.11 wireless LANs. An adversary can exploit this vulnerability to launch a large number of attacks. For example, an attacker may masquerade as a legitimate access point to disrupt network services or to advertise false services, tricking nearby wireless stations. On the other hand, the received signal strength (RSS) is a measurement that is hard to forge arbitrarily and it is highly correlated to the transmitter's location. Assuming the attacker and the victim are separated by a reasonable distance, RSS can be used to differentiate them to detect MAC spoofing, as recently proposed …
Refocusing In 802.11 Wireless Measurement, Udayan Deshpande, Chris Mcdonald, David Kotz
Refocusing In 802.11 Wireless Measurement, Udayan Deshpande, Chris Mcdonald, David Kotz
Dartmouth Scholarship
The edge of the Internet is increasingly wireless. To understand the Internet, one must understand the edge, and yet the measurement of wireless networks poses many new challenges. IEEE 802.11 networks support multiple wireless channels and any monitoring technique involves capturing traffic on each of these channels to gather a representative sample of frames from the network. We call this procedure \emphchannel sampling, in which each sniffer visits each channel periodically, resulting in a sample of the traffic on each of the channels. \par This sampling approach may be sufficient, for example, for a system administrator or anomaly detection module …
Active Behavioral Fingerprinting Of Wireless Devices, Sergey Bratus, Cory Cornelius, David Kotz, Daniel Peebles
Active Behavioral Fingerprinting Of Wireless Devices, Sergey Bratus, Cory Cornelius, David Kotz, Daniel Peebles
Computer Science Technical Reports
We propose a simple active method for discovering facts about the chipset, the firmware or the driver of an 802.11 wireless device by observing its responses (or lack thereof) to a series of crafted non-standard or malformed 802.11 frames. We demonstrate that such responses can differ significantly enough to distinguish between a number of popular chipsets and drivers. We expect to significantly expand the number of recognized device types through community contributions of signature data for the proposed open fingerprinting framework. Our method complements known fingerprinting approaches, and can be used to interrogate and spot devices that may be spoofing …
Active Behavioral Fingerprinting Of Wireless Devices, Sergey Bratus, Cory Cornelius, David Kotz, Dan Peebles
Active Behavioral Fingerprinting Of Wireless Devices, Sergey Bratus, Cory Cornelius, David Kotz, Dan Peebles
Dartmouth Scholarship
We propose a simple active method for discovering facts about the chipset, the firmware or the driver of an 802.11 wireless device by observing its responses (or lack thereof) to a series of crafted non-standard or malformed 802.11 frames. We demonstrate that such responses can differ significantly enough to distinguish between a number of popular chipsets and drivers. We expect to significantly expand the number of recognized device types through community contributions of signature data for the proposed open fingerprinting framework. Our method complements known fingerprinting approaches, and can be used to interrogate and spot devices that may be spoofing …
Localized Bridging Centrality For Distributed Network Analysis, Soumendra Nanda, David Kotz
Localized Bridging Centrality For Distributed Network Analysis, Soumendra Nanda, David Kotz
Computer Science Technical Reports
Centrality is a concept often used in social network analysis to study different properties of networks that are modeled as graphs. We present a new centrality metric called Localized Bridging Centrality (LBC). LBC is based on the Bridging Centrality (BC) metric that Hwang et al. recently introduced. Bridging nodes are nodes that are located in between highly connected regions. LBC is capable of identifying bridging nodes with an accuracy comparable to that of the BC metric for most networks. As the name suggests, we use only local information from surrounding nodes to compute the LBC metric, while, global knowledge is …
Evaluating Mobility Predictors In Wireless Networks For Improving Handoff And Opportunistic Routing, Libo Song
Evaluating Mobility Predictors In Wireless Networks For Improving Handoff And Opportunistic Routing, Libo Song
Dartmouth College Ph.D Dissertations
We evaluate mobility predictors in wireless networks. Handoff prediction in wireless networks has long been considered as a mechanism to improve the quality of service provided to mobile wireless users. Most prior studies, however, were based on theoretical analysis, simulation with synthetic mobility models, or small wireless network traces. We study the effect of mobility prediction for a large realistic wireless situation. We tackle the problem by using traces collected from a large production wireless network to evaluate several major families of handoff-location prediction techniques, a set of handoff-time predictors, and a predictor that jointly predicts handoff location and time. …
Settling For Limited Privacy: How Much Does It Help?, Anna M. Shubina
Settling For Limited Privacy: How Much Does It Help?, Anna M. Shubina
Dartmouth College Ph.D Dissertations
This thesis explores practical and theoretical aspects of several privacy-providing technologies, including tools for anonymous web-browsing, verifiable electronic voting schemes, and private information retrieval from databases. State-of-art privacy-providing schemes are frequently impractical for implementational reasons or for sheer information-theoretical reasons due to the amount of information that needs to be transmitted. We have been researching the question of whether relaxing the requirements on such schemes, in particular settling for imperfect but sufficient in real-world situations privacy, as opposed to perfect privacy, may be helpful in producing more practical or more efficient schemes. This thesis presents three results. The first result …
Two's Company, Three's A Crowd: Stable Family And Threesome Roommates Problems, Chien-Chung Huang
Two's Company, Three's A Crowd: Stable Family And Threesome Roommates Problems, Chien-Chung Huang
Computer Science Technical Reports
We investigate Knuth's eleventh open question on stable matchings. In the stable family problem, sets of women, men, and dogs are given, all of whom state their preferences among the other two groups. The goal is to organize them into family units, so that no three of them have the incentive to desert their assigned family members to form a new family. A similar problem, called the threesome roommates problem, assumes that a group of persons, each with their preferences among the combinations of two others, are to be partitioned into triples. Similarly, the goal is to make sure that …
Exclusion And Object Tracking In A Network Of Processes, Yih-Kuen Tsay, Chien-Chung Huang
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
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
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.
Lighting And Optical Tools For Image Forensics, Micah Kimo Johnson
Lighting And Optical Tools For Image Forensics, Micah Kimo Johnson
Dartmouth College Ph.D Dissertations
We present new forensic tools that are capable of detecting traces of tampering in digital images without the use of watermarks or specialized hardware. These tools operate under the assumption that images contain natural properties from a variety of sources, including the world, the lens, and the sensor. These properties may be disturbed by digital tampering and by measuring them we can expose the forgery. In this context, we present the following forensic tools: (1) illuminant direction, (2) specularity, (3) lighting environment, and (4) chromatic aberration. The common theme of these tools is that they exploit lighting or optical properties …
Video Stabilization And Enhancement, Hany Farid, Jeffrey B. Woodward
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.