CSE Technical Reports Sorted by Technical Report Number
|As mobile devices continue to shrink, users are
no longer merely nomads, but truly mobile,
employing devices on the move. At the same time,
these users no longer rely on a single
managed network, but exploit a wide variety of
connectivity options as they spend their day.
Together, these trends argue that systems must
consider the derivative of connectivity---
the changes inherent in movement between
separately managed networks, with widely varying
To manage the derivative of connectivity, we
exploit the fact that people are creatures of
habit; they take similar paths every day. Our
system, BreadCrumbs, tracks the movement of the
device’s owner, and customizes a predictive
mobility model for that specific user. Rather than
rely on a synthetic model or aggregate
observations, this custom-tailored model can be
used together with past observations of wireless
network capabilities to generate connectivity
forecasts. Applications can in turn use these
forecasts to plan future network use with
confidence. We have built a BreadCrumbs prototype,
and evaluated it with several weeks of real-world
usage. Our results show that these forecasts are
sufficiently accurate, even with as little as one
week of training, to provide improved performance
with reduced power consumption for several
| There are many situations in which an additional network interface---or two---can provide benefits to a mobile user. Additional interfaces can support parallelism in network flows, improve handoff times, and provide sideband communication with nearby peers. Unfortunately, such benefits are outweighed by the added costs of an additional physical interface. Instead, virtual interfaces have been proposed as the solution, multiplexing a single physical interface across more than one communication endpoint. However, the switching time of existing implementations is too high for some potential applications, and the benefits of this approach to real applications are not yet clear. This paper directly addresses these two shortcomings. It describes an implementation of a virtual 802.11 networking layer, called Juggler, that achieves switching times of approximately 3 ms, and less than 400 us in certain conditions. We demonstrate the performance of this implementation on three application scenarios. By devoting 10% of the duty cycle to background tasks, Juggler can provide nearly instantaneous handoff between base stations or support a modest sideband channel with peer nodes, without adversely affecting foreground throughput. Furthermore, when the client issues concurrent network flows, Juggler is able to assign these flows across more than one AP, providing significant speedup when wired-side bandwidth from the AP constrains end-to-end performance.
|The WebBee system is a complete software framework that supports security-sensitive
applications for mobile, handheld devices. Though the WebBee system is designed to support security
for users, there is a critical window of time between when a device is compromised, and when security
is once again established. Security is reestablished by one of two mechanisms. The first is enacted when
the user is able to notify the system of the compromise. Secondly, security will also be reestablished
when the security keys are renewed. In the paper, we introduce a challenge-response system which
is tailored for the WebBee environment to support its unique characteristics. The challenge system
has been designed and implemented on top of the WebBee system so that the system as a whole can
maximize security even in an emergency. The design scheme has been carefully chosen to minimize the
impact on the existing WebBee infrastructure and to integrate with other detection mechanisms easily.
The overall performance of the WebBee system is not affected by the challenge system significantly
because challenges are only assigned in limited numbers.
|The Webbee research project’s mission is to provide a secure coordination and communication
infrastructure to a team of first responders. Our architecture consists of three basic elements:
an instant infrastructure, which restores connectivity; the Webbee Coordination Server,
comprised of application daemons that provide communication and coordination services on
top a secure, mobile handheld-friendly environment; and a Database Server, which serves all
data necessary for interactions, and which is enriched with triggers to automatically take action
when certain new data is supplied to the database. We have successfully deployed several sample
applications using this architecture - such as Gas Prices, Event Reports, and AC2 - so as
to illustrate the architecture’s viability, flexibility, and security, especially in disaster scenario
|We present a method for constructing signature schemes for use with mobile handheld
devices that mitigates the risk of an attacker forging signatures using key material garnered from a
lost handheld. This scheme is forward-secure, meaning that signatures created before a breach are still
valid, and server-assisted, meaning that a separate untrusted server must assist the device in signing,
thereby protecting against offline dictionary attacks. We also present our experience with implementing
these types of signature schemes for Java-enabled mobile devices, and the results of our experiments
with this implementation.
|Information retrieval (IR) is the science of information search within documents, relational databases, and the World Wide Web (WWW). In this work, we have tried to review some novel methods in IR theory. This report covers a number of the state of art methods in a wide range of topics with a focus on graph-based techniques in IR.
This report is created based on the literature review done as a requirement of the Directed Study, EECS 599, course at the Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor. The ﬁrst author would like to thank Prof. Dragomir R. Radev for his discussions, reviews, and useful suggestions to support this work.
|This summarizes some of the common algorithms and approaches used for various tasks in Information Retrieval and Natural Language processing like, Text Summarization, Machine Translation, Sentiment Detection, Dependence Parsing, etc. This report is submitted towards satisfying the requirement of the Directed Study, EECS 599 course, Computer Science division, University of Michigan, Ann Arbor under the supervision of Professor Dragomir R. Radev
|Database provenance chronicles the history of updates and modifications to data, and has received much attention due to its central role in scientific data management. However, the use of provenance information still requires a leap of faith. Without additional protections, provenance records are vulnerable to accidental corruption, and even malicious forgery, a problem that is most pronounced in the loosely-coupled multi-user environments often found in scientific research.
This paper investigates the problem of providing integrity and tamper-detection for database provenance. We propose a checksum-based approach, which is well-suited to the unique characteristics of database provenance, including non-linear provenance objects and provenance associated with multiple fine granularities of data. We demonstrate that the proposed solution satisfies a set of desirable security properties, and that the additional time and space overhead incurred by the checksum approach is manageable, making the solution feasible in practice.
|Searching through a user's distributed data set effectively is crucial. User created content is increasingly stored on multiple devices away from home. Conventional desktop search and distributed file systems have relied on kernel modules and practically unlimited resources to organize and search user content. These designs do not consider the complex set of constraints and challenges in the distributed search domain. We propose a distributed architecture, DSearch, to manage the complexities of a mobile data set to improve query performance across all the devices in a user's personal area network. First, we provide a light-weight infrastructure that can effectively organize and search a set of devices. Second, we develop a membership system to manage the dynamics of multiple devices in a network that records the current set of active devices and distributes information to the group. Third, we examine three search index replication schemes - no replication, centralized replication, and device-based replication - to improve query performance. We developed the DSearch distributed search architecture and evaluated its performance.
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