1,174 research outputs found
Individual Privacy vs Population Privacy: Learning to Attack Anonymization
Over the last decade there have been great strides made in developing
techniques to compute functions privately. In particular, Differential Privacy
gives strong promises about conclusions that can be drawn about an individual.
In contrast, various syntactic methods for providing privacy (criteria such as
kanonymity and l-diversity) have been criticized for still allowing private
information of an individual to be inferred. In this report, we consider the
ability of an attacker to use data meeting privacy definitions to build an
accurate classifier. We demonstrate that even under Differential Privacy, such
classifiers can be used to accurately infer "private" attributes in realistic
data. We compare this to similar approaches for inferencebased attacks on other
forms of anonymized data. We place these attacks on the same scale, and observe
that the accuracy of inference of private attributes for Differentially Private
data and l-diverse data can be quite similar
One Table to Count Them All: Parallel Frequency Estimation on Single-Board Computers
Sketches are probabilistic data structures that can provide approximate
results within mathematically proven error bounds while using orders of
magnitude less memory than traditional approaches. They are tailored for
streaming data analysis on architectures even with limited memory such as
single-board computers that are widely exploited for IoT and edge computing.
Since these devices offer multiple cores, with efficient parallel sketching
schemes, they are able to manage high volumes of data streams. However, since
their caches are relatively small, a careful parallelization is required. In
this work, we focus on the frequency estimation problem and evaluate the
performance of a high-end server, a 4-core Raspberry Pi and an 8-core Odroid.
As a sketch, we employed the widely used Count-Min Sketch. To hash the stream
in parallel and in a cache-friendly way, we applied a novel tabulation approach
and rearranged the auxiliary tables into a single one. To parallelize the
process with performance, we modified the workflow and applied a form of
buffering between hash computations and sketch updates. Today, many
single-board computers have heterogeneous processors in which slow and fast
cores are equipped together. To utilize all these cores to their full
potential, we proposed a dynamic load-balancing mechanism which significantly
increased the performance of frequency estimation.Comment: 12 pages, 4 figures, 3 algorithms, 1 table, submitted to EuroPar'1
Tight Lower Bound for Comparison-Based Quantile Summaries
Quantiles, such as the median or percentiles, provide concise and useful
information about the distribution of a collection of items, drawn from a
totally ordered universe. We study data structures, called quantile summaries,
which keep track of all quantiles, up to an error of at most .
That is, an -approximate quantile summary first processes a stream
of items and then, given any quantile query , returns an item
from the stream, which is a -quantile for some . We focus on comparison-based quantile summaries that can only
compare two items and are otherwise completely oblivious of the universe.
The best such deterministic quantile summary to date, due to Greenwald and
Khanna (SIGMOD '01), stores at most items, where is the number of items in the stream. We prove
that this space bound is optimal by showing a matching lower bound. Our result
thus rules out the possibility of constructing a deterministic comparison-based
quantile summary in space , for any function
that does not depend on . As a corollary, we improve the lower bound for
biased quantiles, which provide a stronger, relative-error guarantee of , and for other related computational tasks.Comment: 20 pages, 2 figures, major revison of the construction (Sec. 3) and
some other parts of the pape
An Improved Interactive Streaming Algorithm for the Distinct Elements Problem
The exact computation of the number of distinct elements (frequency moment
) is a fundamental problem in the study of data streaming algorithms. We
denote the length of the stream by where each symbol is drawn from a
universe of size . While it is well known that the moments can
be approximated by efficient streaming algorithms, it is easy to see that exact
computation of requires space . In previous work, Cormode
et al. therefore considered a model where the data stream is also processed by
a powerful helper, who provides an interactive proof of the result. They gave
such protocols with a polylogarithmic number of rounds of communication between
helper and verifier for all functions in NC. This number of rounds
can quickly make such
protocols impractical.
Cormode et al. also gave a protocol with rounds for the exact
computation of where the space complexity is but the total communication . They managed to give round protocols with
complexity for many other interesting problems
including , Inner product, and Range-sum, but computing exactly with
polylogarithmic space and communication and rounds remained open.
In this work, we give a streaming interactive protocol with rounds
for exact computation of using bits of space and the communication is . The update
time of the verifier per symbol received is .Comment: Submitted to ICALP 201
First Author Advantage: Citation Labeling in Research
Citations among research papers, and the networks they form, are the primary
object of study in scientometrics. The act of making a citation reflects the
citer's knowledge of the related literature, and of the work being cited. We
aim to gain insight into this process by studying citation keys: user-chosen
labels to identify a cited work. Our main observation is that the first listed
author is disproportionately represented in such labels, implying a strong
mental bias towards the first author.Comment: Computational Scientometrics: Theory and Applications at The 22nd
CIKM 201
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