451 research outputs found
Rethinking Location Privacy for Unknown Mobility Behaviors
Location Privacy-Preserving Mechanisms (LPPMs) in the literature largely
consider that users' data available for training wholly characterizes their
mobility patterns. Thus, they hardwire this information in their designs and
evaluate their privacy properties with these same data. In this paper, we aim
to understand the impact of this decision on the level of privacy these LPPMs
may offer in real life when the users' mobility data may be different from the
data used in the design phase. Our results show that, in many cases, training
data does not capture users' behavior accurately and, thus, the level of
privacy provided by the LPPM is often overestimated. To address this gap
between theory and practice, we propose to use blank-slate models for LPPM
design. Contrary to the hardwired approach, that assumes known users' behavior,
blank-slate models learn the users' behavior from the queries to the service
provider. We leverage this blank-slate approach to develop a new family of
LPPMs, that we call Profile Estimation-Based LPPMs. Using real data, we
empirically show that our proposal outperforms optimal state-of-the-art
mechanisms designed on sporadic hardwired models. On non-sporadic location
privacy scenarios, our method is only better if the usage of the location
privacy service is not continuous. It is our hope that eliminating the need to
bootstrap the mechanisms with training data and ensuring that the mechanisms
are lightweight and easy to compute help fostering the integration of location
privacy protections in deployed systems
Is Geo-Indistinguishability What You Are Looking for?
Since its proposal in 2013, geo-indistinguishability has been consolidated as
a formal notion of location privacy, generating a rich body of literature
building on this idea. A problem with most of these follow-up works is that
they blindly rely on geo-indistinguishability to provide location privacy,
ignoring the numerical interpretation of this privacy guarantee. In this paper,
we provide an alternative formulation of geo-indistinguishability as an
adversary error, and use it to show that the privacy vs.~utility trade-off that
can be obtained is not as appealing as implied by the literature. We also show
that although geo-indistinguishability guarantees a lower bound on the
adversary's error, this comes at the cost of achieving poorer performance than
other noise generation mechanisms in terms of average error, and enabling the
possibility of exposing obfuscated locations that are useless from the quality
of service point of view
IHOP: Improved Statistical Query Recovery against Searchable Symmetric Encryption through Quadratic Optimization
Effective query recovery attacks against Searchable Symmetric Encryption
(SSE) schemes typically rely on auxiliary ground-truth information about the
queries or dataset. Query recovery is also possible under the weaker
statistical auxiliary information assumption, although statistical-based
attacks achieve lower accuracy and are not considered a serious threat. In this
work we present IHOP, a statistical-based query recovery attack that formulates
query recovery as a quadratic optimization problem and reaches a solution by
iterating over linear assignment problems. We perform an extensive evaluation
with five real datasets, and show that IHOP outperforms all other
statistical-based query recovery attacks under different parameter and leakage
configurations, including the case where the client uses some access-pattern
obfuscation defenses. In some cases, our attack achieves almost perfect query
recovery accuracy. Finally, we use IHOP in a frequency-only leakage setting
where the client's queries are correlated, and show that our attack can exploit
query dependencies even when PANCAKE, a recent frequency-hiding defense by
Grubbs et al., is applied. Our findings indicate that statistical query
recovery attacks pose a severe threat to privacy-preserving SSE schemes.Comment: 18 page
Radio Observations of the Region around the Pulsar Wind Nebula HESS J1303-631 with ATCA
Radio observations of the region surrounding PSR J1301-6305 at 5.5 GHz and
7.5 GHz were conducted with ATCA on September 5th, 2013. They were dedicated to
the search of the radio counterpart of the evolved pulsar wind nebula HESS
J1303-631, detected in X-rays and GeV-TeV gamma-rays. The collected data do not
reveal any significant extended emission associated with PSR J1301-6305. In
addition, archival 1.384 GHz and 2.368 GHz data do not show any evidence for a
radio counterpart of HESS J1303-631. Archival 1.384 GHz observations reveal a
detection of an extended structure centred at an angular distance of 190 from
the pulsar. This extended structure might be a Supernova remnant (SNR) and a
potential birth place of PSR J1301-6305. The implications of the lack of radio
counterpart of HESS J1303-631 on the understanding of the nature of the PWN are
discussed.Comment: 7 pages, 4 figures, 2 tables, accepted for publication in A&
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