3,857 research outputs found
Chaotic Compilation for Encrypted Computing: Obfuscation but Not in Name
An `obfuscation' for encrypted computing is quantified exactly here, leading
to an argument that security against polynomial-time attacks has been achieved
for user data via the deliberately `chaotic' compilation required for security
properties in that environment. Encrypted computing is the emerging science and
technology of processors that take encrypted inputs to encrypted outputs via
encrypted intermediate values (at nearly conventional speeds). The aim is to
make user data in general-purpose computing secure against the operator and
operating system as potential adversaries. A stumbling block has always been
that memory addresses are data and good encryption means the encrypted value
varies randomly, and that makes hitting any target in memory problematic
without address decryption, yet decryption anywhere on the memory path would
open up many easily exploitable vulnerabilities. This paper `solves (chaotic)
compilation' for processors without address decryption, covering all of ANSI C
while satisfying the required security properties and opening up the field for
the standard software tool-chain and infrastructure. That produces the argument
referred to above, which may also hold without encryption.Comment: 31 pages. Version update adds "Chaotic" in title and throughout
paper, and recasts abstract and Intro and other sections of the text for
better access by cryptologists. To the same end it introduces the polynomial
time defense argument explicitly in the final section, having now set that
denouement out in the abstract and intr
Programmiersprachen und Rechenkonzepte
Seit 1984 veranstaltet die GI-Fachgruppe "Programmiersprachen und Rechenkonzepte" regelmäßig im Frühjahr einen Workshop im Physikzentrum Bad Honnef. Das Treffen dient in erster Linie dem gegenseitigen Kennenlernen, dem Erfahrungsaustausch, der Diskussion und der Vertiefung gegenseitiger Kontakte. In diesem Forum werden Vorträge und Demonstrationen sowohl bereits abgeschlossener als auch noch laufender Arbeiten vorgestellt, unter anderem (aber nicht ausschließlich) zu Themen wie - Sprachen, Sprachparadigmen, - Korrektheit von Entwurf und Implementierung, -Werkzeuge, -Software-/Hardware-Architekturen, -Spezifikation, Entwurf, - Validierung, Verifikation, - Implementierung, Integration, - Sicherheit (Safety und Security), - eingebettete Systeme, - hardware-nahe Programmierung. In diesem Technischen Bericht sind einige der präsentierten Arbeiten zusammen gestellt
[Nine Book Reviews]
Death Inside Out: The Hastings Center Report, edited by Peter Steinfels and Robert M. Veatch. Living and Dying at Murray Manor, by Jaber E. Gubrium. How to Face Death Without Fear: Selections from the book Preparation for Death by St. Alphonsus Liguori, edited by Norman J. Muckerman. The Dilemmas of Euthanasia, edited by John A. Behnke and Sissela Bok. Death and Beyond, by Andrew Greeley. Handbook on Euthanasia, by Susan M. and Robert L. Sassone. The Release of the Destruction of Life Devoid of Value, by Karl Binding and Alfred Hoche, with comments by Robert L. Sassone. The Myth of the Hyperactive Child and Other Means of Child Control, by Peter Schrag and Diane Divoky. Genetic Screening: Programs, Principles and Research, by Barton Childs et al
Array operators using multiple dispatch: a design methodology for array implementations in dynamic languages
Arrays are such a rich and fundamental data type that they tend to be built
into a language, either in the compiler or in a large low-level library.
Defining this functionality at the user level instead provides greater
flexibility for application domains not envisioned by the language designer.
Only a few languages, such as C++ and Haskell, provide the necessary power to
define -dimensional arrays, but these systems rely on compile-time
abstraction, sacrificing some flexibility. In contrast, dynamic languages make
it straightforward for the user to define any behavior they might want, but at
the possible expense of performance.
As part of the Julia language project, we have developed an approach that
yields a novel trade-off between flexibility and compile-time analysis. The
core abstraction we use is multiple dispatch. We have come to believe that
while multiple dispatch has not been especially popular in most kinds of
programming, technical computing is its killer application. By expressing key
functions such as array indexing using multi-method signatures, a surprising
range of behaviors can be obtained, in a way that is both relatively easy to
write and amenable to compiler analysis. The compact factoring of concerns
provided by these methods makes it easier for user-defined types to behave
consistently with types in the standard library.Comment: 6 pages, 2 figures, workshop paper for the ARRAY '14 workshop, June
11, 2014, Edinburgh, United Kingdo
Theory and Algorithms for Partial Order Based Reduction in Planning
Search is a major technique for planning. It amounts to exploring a state
space of planning domains typically modeled as a directed graph. However,
prohibitively large sizes of the search space make search expensive. Developing
better heuristic functions has been the main technique for improving search
efficiency. Nevertheless, recent studies have shown that improving heuristics
alone has certain fundamental limits on improving search efficiency. Recently,
a new direction of research called partial order based reduction (POR) has been
proposed as an alternative to improving heuristics. POR has shown promise in
speeding up searches.
POR has been extensively studied in model checking research and is a key
enabling technique for scalability of model checking systems. Although the POR
theory has been extensively studied in model checking, it has never been
developed systematically for planning before. In addition, the conditions for
POR in the model checking theory are abstract and not directly applicable in
planning. Previous works on POR algorithms for planning did not establish the
connection between these algorithms and existing theory in model checking.
In this paper, we develop a theory for POR in planning. The new theory we
develop connects the stubborn set theory in model checking and POR methods in
planning. We show that previous POR algorithms in planning can be explained by
the new theory. Based on the new theory, we propose a new, stronger POR
algorithm. Experimental results on various planning domains show further search
cost reduction using the new algorithm
A new parallelisation technique for heterogeneous CPUs
Parallelization has moved in recent years into the mainstream compilers, and the demand
for parallelizing tools that can do a better job of automatic parallelization is higher than
ever. During the last decade considerable attention has been focused on developing programming
tools that support both explicit and implicit parallelism to keep up with the
power of the new multiple core technology. Yet the success to develop automatic parallelising
compilers has been limited mainly due to the complexity of the analytic process
required to exploit available parallelism and manage other parallelisation measures such
as data partitioning, alignment and synchronization.
This dissertation investigates developing a programming tool that automatically parallelises
large data structures on a heterogeneous architecture and whether a high-level programming
language compiler can use this tool to exploit implicit parallelism and make use
of the performance potential of the modern multicore technology. The work involved the
development of a fully automatic parallelisation tool, called VSM, that completely hides
the underlying details of general purpose heterogeneous architectures. The VSM implementation
provides direct and simple access for users to parallelise array operations on the
Cell’s accelerators without the need for any annotations or process directives. This work
also involved the extension of the Glasgow Vector Pascal compiler to work with the VSM
implementation as a one compiler system. The developed compiler system, which is called
VP-Cell, takes a single source code and parallelises array expressions automatically.
Several experiments were conducted using Vector Pascal benchmarks to show the validity
of the VSM approach. The VP-Cell system achieved significant runtime performance
on one accelerator as compared to the master processor’s performance and near-linear
speedups over code runs on the Cell’s accelerators. Though VSM was mainly designed for
developing parallelising compilers it also showed a considerable performance by running
C code over the Cell’s accelerators
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