2,815 research outputs found
"On the Road" - Reflections on the Security of Vehicular Communication Systems
Vehicular communication (VC) systems have recently drawn the attention of
industry, authorities, and academia. A consensus on the need to secure VC
systems and protect the privacy of their users led to concerted efforts to
design security architectures. Interestingly, the results different project
contributed thus far bear extensive similarities in terms of objectives and
mechanisms. As a result, this appears to be an auspicious time for setting the
corner-stone of trustworthy VC systems. Nonetheless, there is a considerable
distance to cover till their deployment. This paper ponders on the road ahead.
First, it presents a distillation of the state of the art, covering the
perceived threat model, security requirements, and basic secure VC system
components. Then, it dissects predominant assumptions and design choices and
considers alternatives. Under the prism of what is necessary to render secure
VC systems practical, and given possible non-technical influences, the paper
attempts to chart the landscape towards the deployment of secure VC systems
Algorithms for Fast Aggregated Convergecast in Sensor Networks
Fast and periodic collection of aggregated data
is of considerable interest for mission-critical and continuous
monitoring applications in sensor networks. In the many-to-one
communication paradigm, referred to as convergecast, we focus
on applications wherein data packets are aggregated at each hop
en-route to the sink along a tree-based routing topology, and
address the problem of minimizing the convergecast schedule
length by utilizing multiple frequency channels. The primary
hindrance in minimizing the schedule length is the presence of
interfering links. We prove that it is NP-complete to determine
whether all the interfering links in an arbitrary network can
be removed using at most a constant number of frequencies.
We give a sufficient condition on the number of frequencies for
which all the interfering links can be removed, and propose a
polynomial time algorithm that minimizes the schedule length
in this case. We also prove that minimizing the schedule length
for a given number of frequencies on an arbitrary network is
NP-complete, and describe a greedy scheme that gives a constant
factor approximation on unit disk graphs. When the routing tree
is not given as an input to the problem, we prove that a constant
factor approximation is still achievable for degree-bounded trees.
Finally, we evaluate our algorithms through simulations and
compare their performance under different network parameters
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