120,947 research outputs found
CapablePtrs: Securely Compiling Partial Programs using the Pointers-as-Capabilities Principle
Capability machines such as CHERI provide memory capabilities that can be
used by compilers to provide security benefits for compiled code (e.g., memory
safety). The C to CHERI compiler, for example, achieves memory safety by
following a principle called "pointers as capabilities" (PAC). Informally, PAC
says that a compiler should represent a source language pointer as a machine
code capability. But the security properties of PAC compilers are not yet well
understood. We show that memory safety is only one aspect, and that PAC
compilers can provide significant additional security guarantees for partial
programs: the compiler can provide guarantees for a compilation unit, even if
that compilation unit is later linked to attacker-controlled machine code. This
paper is the first to study the security of PAC compilers for partial programs
formally. We prove for a model of such a compiler that it is fully abstract.
The proof uses a novel proof technique (dubbed TrICL, read trickle), which is
of broad interest because it reuses and extends the compiler correctness
relation in a natural way, as we demonstrate. We implement our compiler on top
of the CHERI platform and show that it can compile legacy C code with minimal
code changes. We provide performance benchmarks that show how performance
overhead is proportional to the number of cross-compilation-unit function
calls
Modeling relation paths for knowledge base completion via joint adversarial training
Knowledge Base Completion (KBC), which aims at determining the missing
relations between entity pairs, has received increasing attention in recent
years. Most existing KBC methods focus on either embedding the Knowledge Base
(KB) into a specific semantic space or leveraging the joint probability of
Random Walks (RWs) on multi-hop paths. Only a few unified models take both
semantic and path-related features into consideration with adequacy. In this
paper, we propose a novel method to explore the intrinsic relationship between
the single relation (i.e. 1-hop path) and multi-hop paths between paired
entities. We use Hierarchical Attention Networks (HANs) to select important
relations in multi-hop paths and encode them into low-dimensional vectors. By
treating relations and multi-hop paths as two different input sources, we use a
feature extractor, which is shared by two downstream components (i.e. relation
classifier and source discriminator), to capture shared/similar information
between them. By joint adversarial training, we encourage our model to extract
features from the multi-hop paths which are representative for relation
completion. We apply the trained model (except for the source discriminator) to
several large-scale KBs for relation completion. Experimental results show that
our method outperforms existing path information-based approaches. Since each
sub-module of our model can be well interpreted, our model can be applied to a
large number of relation learning tasks.Comment: Accepted by Knowledge-Based System
FIXES, a system for automatic selection of set-ups and design of fixtures
This paper reports on the development of a computer aided planning system for the selection of set-ups and the design of fixtures in part manufacturing. First, the bottlenecks in the present planning methods are indicated. A brief description is given of the CAPP environment PART, in which FIXES is incorporated. The planning procedure of FIXES consists of two parts: the selection of set-ups and the design of a fixture for each set-up. The automatic selection of set-ups is based on the comparison of the tolerances of the relations between the different shape elements of the part. A tolerance factor has been developed to be able to compare the different tolerances. The system automatically selects the positioning faces and supports the selection of tools for positioning, clamping and supporting the part. A prototype implementation of FIXES is discussed
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