3,247 research outputs found
Practical Fine-grained Privilege Separation in Multithreaded Applications
An inherent security limitation with the classic multithreaded programming
model is that all the threads share the same address space and, therefore, are
implicitly assumed to be mutually trusted. This assumption, however, does not
take into consideration of many modern multithreaded applications that involve
multiple principals which do not fully trust each other. It remains challenging
to retrofit the classic multithreaded programming model so that the security
and privilege separation in multi-principal applications can be resolved.
This paper proposes ARBITER, a run-time system and a set of security
primitives, aimed at fine-grained and data-centric privilege separation in
multithreaded applications. While enforcing effective isolation among
principals, ARBITER still allows flexible sharing and communication between
threads so that the multithreaded programming paradigm can be preserved. To
realize controlled sharing in a fine-grained manner, we created a novel
abstraction named ARBITER Secure Memory Segment (ASMS) and corresponding OS
support. Programmers express security policies by labeling data and principals
via ARBITER's API following a unified model. We ported a widely-used, in-memory
database application (memcached) to ARBITER system, changing only around 100
LOC. Experiments indicate that only an average runtime overhead of 5.6% is
induced to this security enhanced version of application
A Socially-Aware Incentive Mechanism for Mobile Crowdsensing Service Market
Mobile Crowdsensing has shown a great potential to address large-scale
problems by allocating sensing tasks to pervasive Mobile Users (MUs). The MUs
will participate in a Crowdsensing platform if they can receive satisfactory
reward. In this paper, in order to effectively and efficiently recruit
sufficient MUs, i.e., participants, we investigate an optimal reward mechanism
of the monopoly Crowdsensing Service Provider (CSP). We model the rewarding and
participating as a two-stage game, and analyze the MUs' participation level and
the CSP's optimal reward mechanism using backward induction. At the same time,
the reward is designed taking the underlying social network effects amid the
mobile social network into account, for motivating the participants. Namely,
one MU will obtain additional benefits from information contributed or shared
by local neighbours in social networks. We derive the analytical expressions
for the discriminatory reward as well as uniform reward with complete
information, and approximations of reward incentive with incomplete
information. Performance evaluation reveals that the network effects
tremendously stimulate higher mobile participation level and greater revenue of
the CSP. In addition, the discriminatory reward enables the CSP to extract
greater surplus from this Crowdsensing service market.Comment: 7 pages, accepted by IEEE Globecom'1
Tip induced unconventional superconductivity on Weyl semimetal TaAs
Weyl fermion is a massless Dirac fermion with definite chirality, which has
been long pursued since 1929. Though it has not been observed as a fundamental
particle in nature, Weyl fermion can be realized as low-energy excitation
around Weyl point in Weyl semimetal, which possesses Weyl fermion cones in the
bulk and nontrivial Fermi arc states on the surface. As a firstly discovered
Weyl semimetal, TaAs crystal possesses 12 pairs of Weyl points in the momentum
space, which are topologically protected against small perturbations. Here, we
report for the first time the tip induced superconductivity on TaAs crystal by
point contact spectroscopy. A conductance plateau and sharp double dips are
observed in the point contact spectra, indicating p-wave like unconventional
superconductivity. Furthermore, the zero bias conductance peak in low
temperature regime is detected, suggesting potentially the existence of
Majorana zero modes. The experimentally observed tunneling spectra can be
interpreted with a novel mirror-symmetry protected topological superconductor
induced in TaAs, which can exhibit zero bias and double finite bias peaks, and
double conductance dips in the measurements. Our work can open a broad avenue
in search for new topological superconducting phases from topological Weyl
materials and trigger intensive investigations for pursuing Majorana fermions
- …