41,970 research outputs found
The Lazarus Project. II. Spacelike extraction with the quasi-Kinnersley tetrad
The Lazarus project was designed to make the most of limited 3D binary
black-hole simulations, through the identification of perturbations at late
times, and subsequent evolution of the Weyl scalar via the Teukolsky
formulation. Here we report on new developments, employing the concept of the
``quasi-Kinnersley'' (transverse) frame, valid in the full nonlinear regime, to
analyze late-time numerical spacetimes that should differ only slightly from
Kerr. This allows us to extract the essential information about the background
Kerr solution, and through this, to identify the radiation present. We
explicitly test this procedure with full numerical evolutions of Bowen-York
data for single spinning black holes, head-on and orbiting black holes near the
ISCO regime. These techniques can be compared with previous Lazarus results,
providing a measure of the numerical-tetrad errors intrinsic to the method, and
give as a by-product a more robust wave extraction method for numerical
relativity.Comment: 17 pages, 10 figures. Journal version with text changes, revised
figures. [Note updated version of original Lazarus paper (gr-qc/0104063)
The Lazarus Effect: Healing Compromised Devices in the Internet of Small Things
We live in a time when billions of IoT devices are being deployed and
increasingly relied upon. This makes ensuring their availability and
recoverability in case of a compromise a paramount goal. The large and rapidly
growing number of deployed IoT devices make manual recovery impractical,
especially if the devices are dispersed over a large area. Thus, there is a
need for a reliable and scalable remote recovery mechanism that works even
after attackers have taken full control over devices, possibly misusing them or
trying to render them useless.
To tackle this problem, we present Lazarus, a system that enables the remote
recovery of compromised IoT devices. With Lazarus, an IoT administrator can
remotely control the code running on IoT devices unconditionally and within a
guaranteed time bound. This makes recovery possible even in case of severe
corruption of the devices' software stack. We impose only minimal hardware
requirements, making Lazarus applicable even for low-end constrained
off-the-shelf IoT devices. We isolate Lazarus's minimal recovery trusted
computing base from untrusted software both in time and by using a trusted
execution environment. The temporal isolation prevents secrets from being
leaked through side-channels to untrusted software. Inside the trusted
execution environment, we place minimal functionality that constrains untrusted
software at runtime.
We implement Lazarus on an ARM Cortex-M33-based microcontroller in a full
setup with an IoT hub, device provisioning and secure update functionality. Our
prototype can recover compromised embedded OSs and bare-metal applications and
prevents attackers from bricking devices, for example, through flash wear out.
We show this at the example of FreeRTOS, which requires no modifications but
only a single additional task. Our evaluation shows negligible runtime
performance impact and moderate memory requirements.Comment: In Proceedings of the 15th ACM Asia Conference on Computer and
Communications Security (ASIA CCS 20
ОСНОВЫ РАБОТЫ С ГРАФИЧЕСКИМИ ИЗОБРАЖЕНИЯМИ В СИСТЕМЕ ОБЪЕКТНО-ОРИЕНТИРОВАННОГО ПРОГРАММИРОВАНИЯ
В статье представлена разработка элективных курсов по объектно-ориентированному программированию для работы с графическим интерфейсом в средах: Lazarus и Delphi. Представленные технологии позволяет создавать код программы с помощью графических элементов.The article offers the elective course development of object-oriented programming for the graphical interface in the following development environment: Lazarus and Delphi. The presented technologies allow creating program code by using graphical elements.236-24
Radiation tails and boundary conditions for black hole evolutions
In numerical computations of Einstein's equations for black hole spacetimes,
it will be necessary to use approximate boundary conditions at a finite
distance from the holes. We point out here that ``tails,'' the inverse
power-law decrease of late-time fields, cannot be expected for such
computations. We present computational demonstrations and discussions of
features of late-time behavior in an evolution with a boundary condition.Comment: submitted to Phys. Rev.
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