1,026 research outputs found
Systemization of Pluggable Transports for Censorship Resistance
An increasing number of countries implement Internet censorship at different
scales and for a variety of reasons. In particular, the link between the
censored client and entry point to the uncensored network is a frequent target
of censorship due to the ease with which a nation-state censor can control it.
A number of censorship resistance systems have been developed thus far to help
circumvent blocking on this link, which we refer to as link circumvention
systems (LCs). The variety and profusion of attack vectors available to a
censor has led to an arms race, leading to a dramatic speed of evolution of
LCs. Despite their inherent complexity and the breadth of work in this area,
there is no systematic way to evaluate link circumvention systems and compare
them against each other. In this paper, we (i) sketch an attack model to
comprehensively explore a censor's capabilities, (ii) present an abstract model
of a LC, a system that helps a censored client communicate with a server over
the Internet while resisting censorship, (iii) describe an evaluation stack
that underscores a layered approach to evaluate LCs, and (iv) systemize and
evaluate existing censorship resistance systems that provide link
circumvention. We highlight open challenges in the evaluation and development
of LCs and discuss possible mitigations.Comment: Content from this paper was published in Proceedings on Privacy
Enhancing Technologies (PoPETS), Volume 2016, Issue 4 (July 2016) as "SoK:
Making Sense of Censorship Resistance Systems" by Sheharbano Khattak, Tariq
Elahi, Laurent Simon, Colleen M. Swanson, Steven J. Murdoch and Ian Goldberg
(DOI 10.1515/popets-2016-0028
Modeling Probability of Path Loss for DSDV, OLSR and DYMO above 802.11 and 802.11p
This paper presents path loss model along with framework for probability
distribution function for VANETs. Furthermore, we simulate three routing
protocols Destination Sequenced Distance Vector (DSDV), Optimized Link State
Routing (OLSR) and Dynamic MANET On-demand (DYMO) in NS-2 to evaluate and
compare their performance using two Mac-layer Protocols 802.11 and 802.11p. A
novel approach of this work is modifications in existing parameters to achieve
high efficiency. After extensive simulations, we observe that DSDV out performs
with 802.11p while DYMO gives best performance with 802.11.Comment: IEEE 8th International Conference on Broadband and Wireless
Computing, Communication and Applications (BWCCA'13), Compiegne, Franc
Heterogeneous Ensemble Learning for Enhanced Crash Forecasts -- A Frequentest and Machine Learning based Stacking Framework
A variety of statistical and machine learning methods are used to model crash
frequency on specific roadways with machine learning methods generally having a
higher prediction accuracy. Recently, heterogeneous ensemble methods (HEM),
including stacking, have emerged as more accurate and robust intelligent
techniques and are often used to solve pattern recognition problems by
providing more reliable and accurate predictions. In this study, we apply one
of the key HEM methods, Stacking, to model crash frequency on five lane
undivided segments (5T) of urban and suburban arterials. The prediction
performance of Stacking is compared with parametric statistical models (Poisson
and negative binomial) and three state of the art machine learning techniques
(Decision tree, random forest, and gradient boosting), each of which is termed
as the base learner. By employing an optimal weight scheme to combine
individual base learners through stacking, the problem of biased predictions in
individual base-learners due to differences in specifications and prediction
accuracies is avoided. Data including crash, traffic, and roadway inventory
were collected and integrated from 2013 to 2017. The data are split into
training, validation, and testing datasets. Estimation results of statistical
models reveal that besides other factors, crashes increase with density (number
per mile) of different types of driveways. Comparison of out-of-sample
predictions of various models confirms the superiority of Stacking over the
alternative methods considered. From a practical standpoint, stacking can
enhance prediction accuracy (compared to using only one base learner with a
particular specification). When applied systemically, stacking can help
identify more appropriate countermeasures.Comment: This paper was presented at the 101st Transportation Research Board
Annual Meeting (TRBAM) by National Academy of Sciences in January 2022 in
Washington D.C. The paper is currently under review for potential publication
in an Impact Factor Journa
Safety and Economic Assessment of Converting Two-Way Stop-Controlled Intersections to Roundabouts on High Speed Rural Highways
This research addressed two questions: “Are roundabouts on rural high-speed roadways safer than two-way stop controlled (TWSC) intersections?” and “What economic benefits can be expected from converting TWSC intersections to roundabouts in terms of safety improvement?” Crash and traffic data on four TWSC intersections that were converted to roundabouts in Kansas were analyzed using the empirical Bayes before-after evaluation method and crash costs were applied to evaluate economic benefits. Analysis showed that fatal, non-fatal, and property-damage-only crashes were reduced by 100%, 76.47%, and 35.49%, respectively. The annual monetary value from this reduction was between 1.6 million in 2014 dollars
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