11,523 research outputs found
AdSplit: Separating smartphone advertising from applications
A wide variety of smartphone applications today rely on third-party
advertising services, which provide libraries that are linked into the hosting
application. This situation is undesirable for both the application author and
the advertiser. Advertising libraries require additional permissions, resulting
in additional permission requests to users. Likewise, a malicious application
could simulate the behavior of the advertising library, forging the user's
interaction and effectively stealing money from the advertiser. This paper
describes AdSplit, where we extended Android to allow an application and its
advertising to run as separate processes, under separate user-ids, eliminating
the need for applications to request permissions on behalf of their advertising
libraries.
We also leverage mechanisms from Quire to allow the remote server to validate
the authenticity of client-side behavior. In this paper, we quantify the degree
of permission bloat caused by advertising, with a study of thousands of
downloaded apps. AdSplit automatically recompiles apps to extract their ad
services, and we measure minimal runtime overhead. We also observe that most ad
libraries just embed an HTML widget within and describe how AdSplit can be
designed with this in mind to avoid any need for ads to have native code
Shatter cones: Diagnostic impact signatures
Uniquely fractured target rocks known as shatter cones are associated with more than one half the world's 120 or so presently known impact structures. Shatter cones are a form of tensile rock failure in which a positive conical plug separates from a negative outer cup or mold and delicate ornaments radiating from an apex are preserved on surfaces of both portions. Although distinct, shatter cones are sometimes confused with other striated geologic features such as ventifacts, stylolites, cone-in-cone, slickensides, and artificial blast plumes. Complete cones or solitary cones are rare, occurrences are usually as swarms in thoroughly fractured rock. Shatter cones may form in a zone where an expanding shock wave propagating through a target decays to form an elastic wave. Near this transition zone, the expanding primary wave may strike a pebble or other inhomogeneity whose contrasting transmission properties produce a scattered secondary wave. Interference between primary and secondary scattered waves produce conical stress fields with axes perpendicular to the plane of an advancing shock front. This model supports mechanism capable of producing such shatter cone properties as orientation, apical clasts, lithic dependence, and shock pressure zonation. Although formational mechanics are still poorly understood, shatter cones have become the simplest geologic field criterion for recognizing astroblemes (ancient terrestrial impact structures)
Extremal transmission through a microwave photonic crystal and the observation of edge states in a rectangular Dirac billiard
This article presents experimental results on properties of waves propagating
in an unbounded and a bounded photonic crystal consisting of metallic cylinders
which are arranged in a triangular lattice. First, we present transmission
measurements of plane waves traversing a photonic crystal. The experiments are
performed in the vicinity of a Dirac point, i.e., an isolated conical
singularity of the photonic band structure. There, the transmission shows a
pseudodiffusive 1/L dependence, with being the thickness of the crystal, a
phenomenon also observed in graphene. Second, eigenmode intensity distributions
measured in a microwave analog of a relativistic Dirac billiard, a rectangular
microwave billiard that contains a photonic crystal, are discussed. Close to
the Dirac point states have been detected which are localized at the straight
edge of the photonic crystal corresponding to a zigzag edge in graphene
Classical gravitational spin-spin interaction
I obtain an exact, axially symmetric, stationary solution of Einstein's
equations for two massless spinning particles. The term representing the
spin-spin interaction agrees with recently published approximate work. The
spin-spin force appears to be proportional to the inverse fourth power of the
coordinate distance between the particles.Comment: six pages, no figures, journal ref:accepted for Classical and Quantum
Gravit
Application of a trace formula to the spectra of flat three-dimensional dielectric resonators
The length spectra of flat three-dimensional dielectric resonators of
circular shape were determined from a microwave experiment. They were compared
to a semiclassical trace formula obtained within a two-dimensional model based
on the effective index of refraction approximation and a good agreement was
found. It was necessary to take into account the dispersion of the effective
index of refraction for the two-dimensional approximation. Furthermore, small
deviations between the experimental length spectrum and the trace formula
prediction were attributed to the systematic error of the effective index of
refraction approximation. In summary, the methods developed in this article
enable the application of the trace formula for two-dimensional dielectric
resonators also to realistic, flat three-dimensional dielectric microcavities
and -lasers, allowing for the interpretation of their spectra in terms of
classical periodic orbits.Comment: 13 pages, 12 figures, 1 tabl
Quire: Lightweight Provenance for Smart Phone Operating Systems
Smartphone apps often run with full privileges to access the network and
sensitive local resources, making it difficult for remote systems to have any
trust in the provenance of network connections they receive. Even within the
phone, different apps with different privileges can communicate with one
another, allowing one app to trick another into improperly exercising its
privileges (a Confused Deputy attack). In Quire, we engineered two new security
mechanisms into Android to address these issues. First, we track the call chain
of IPCs, allowing an app the choice of operating with the diminished privileges
of its callers or to act explicitly on its own behalf. Second, a lightweight
signature scheme allows any app to create a signed statement that can be
verified anywhere inside the phone. Both of these mechanisms are reflected in
network RPCs, allowing remote systems visibility into the state of the phone
when an RPC is made. We demonstrate the usefulness of Quire with two example
applications. We built an advertising service, running distinctly from the app
which wants to display ads, which can validate clicks passed to it from its
host. We also built a payment service, allowing an app to issue a request which
the payment service validates with the user. An app cannot not forge a payment
request by directly connecting to the remote server, nor can the local payment
service tamper with the request
Experimental Observation of Localized Modes in a Dielectric Square Resonator
We investigated the frequency spectra and field distributions of a dielectric
square resonator in a microwave experiment. Since such systems cannot be
treated analytically, the experimental studies of their properties are
indispensable. The momentum representation of the measured field distributions
shows that all resonant modes are localized on specific classical tori of the
square billiard. Based on these observations a semiclassical model was
developed. It shows excellent agreement with all but a single class of measured
field distributions that will be treated separately.Comment: 6 pages, 5 figures, 1 tabl
Deep scattering layer in the Pacific and Antarctic Oceans
During Operation HIGHJUMP (U. S. Navy Antarctic Development Project, 1947), the writer frequently noted the presence of a layer of deep scatterers on the fathogram of the USS HENDERSON. This layer partially scatters the outgoing sound signal of the recording echo sounder during daylight hours so that a reflection is recorded which has the appearance of a false bottom at various depths between 150 and 450 fathoms
Breeding Oats Resistant to Puccinia graminis avenae
A test of some three hundred oat varieties showed some susceptible and some resistant to Puccinia graminis avenae. A study of the inheritance of resistance has been made by determining the response of hybrids of resistant x susceptible varieties. In this study, Iowa 105 was found to possess a marked resistance in addition to maturing early and thus escaping stem rust. Green Russian and Raukura were both resistant. The F1 generation of Iowa 105 x Green Russian was resistant. The F2 generation gave a wide ratio of several hundred resistant plants to one susceptible. In the F1 progeny test the susceptible F2 plants bred true for susceptibility, while numerous progenies from the resistant F2 plants, segregated into resistant and susceptible plants. Such a wide ratio exists in the F2 generation it is impossible to determine the true factorial basis of inheritance without further work. It is probable, however, that several factors are responsible for the inheritance of resistance to stem rust of oats. These data were further confirmed by the Raukura x Green Russian crosses
- …