403 research outputs found
Lockdown: Dynamic Control-Flow Integrity
Applications written in low-level languages without type or memory safety are
especially prone to memory corruption. Attackers gain code execution
capabilities through such applications despite all currently deployed defenses
by exploiting memory corruption vulnerabilities. Control-Flow Integrity (CFI)
is a promising defense mechanism that restricts open control-flow transfers to
a static set of well-known locations. We present Lockdown, an approach to
dynamic CFI that protects legacy, binary-only executables and libraries.
Lockdown adaptively learns the control-flow graph of a running process using
information from a trusted dynamic loader. The sandbox component of Lockdown
restricts interactions between different shared objects to imported and
exported functions by enforcing fine-grained CFI checks. Our prototype
implementation shows that dynamic CFI results in low performance overhead.Comment: ETH Technical Repor
Collapse of an ecological network in Ancient Egypt
The dynamics of ecosystem collapse are fundamental to determining how and why
biological communities change through time, as well as the potential effects of
extinctions on ecosystems. Here we integrate depictions of mammals from
Egyptian antiquity with direct lines of paleontological and archeological
evidence to infer local extinctions and community dynamics over a 6000-year
span. The unprecedented temporal resolution of this data set enables
examination of how the tandem effects of human population growth and climate
change can disrupt mammalian communities. We show that the extinctions of
mammals in Egypt were nonrandom, and that destabilizing changes in community
composition coincided with abrupt aridification events and the attendant
collapses of some complex societies. We also show that the roles of species in
a community can change over time, and that persistence is predicted by measures
of species sensitivity, a function of local dynamic stability. Our study is the
first high-resolution analysis of the ecological impacts of environmental
change on predator-prey networks over millennial timescales, and sheds light on
the historical events that have shaped modern animal communities
Magnetic microstructure and magnetotransport in Co2FeAl Heusler compound thin films
We correlate simultaneously recorded magnetotransport and spatially resolved
magneto optical Kerr effect (MOKE) data in Co2FeAl Heusler compound thin films
micropatterned into Hall bars. Room temperature MOKE images reveal the
nucleation and propagation of domains in an externally applied magnetic field
and are used to extract a macrospin corresponding to the mean magnetization
direction in the Hall bar. The anisotropic magnetoresistance calculated using
this macrospin is in excellent agreement with magnetoresistance measurements.
This suggests that the magnetotransport in Heusler compounds can be adequately
simulated using simple macrospin models, while the magnetoresistance
contribution due to domain walls is of negligible importance
Exchange-enhanced Ultrastrong Magnon-Magnon Coupling in a Compensated Ferrimagnet
The ultrastrong coupling of (quasi-)particles has gained considerable
attention due to its application potential and richness of the underlying
physics. Coupling phenomena arising due to electromagnetic interactions are
well explored. In magnetically ordered systems, the quantum-mechanical
exchange-interaction should furthermore enable a fundamentally different
coupling mechanism. Here, we report the observation of ultrastrong intralayer
exchange-enhanced magnon-magnon coupling in a compensated ferrimagnet. We
experimentally study the spin dynamics in a gadolinium iron garnet single
crystal using broadband ferromagnetic resonance. Close to the ferrimagnetic
compensation temperature, we observe ultrastrong coupling of clockwise and
anticlockwise magnon modes. The magnon-magnon coupling strength reaches more
than 30% of the mode frequency and can be tuned by varying the direction of the
external magnetic field. We theoretically explain the observed phenomenon in
terms of an exchange-enhanced mode-coupling mediated by a weak cubic
anisotropy
- …