Generating large non-singular matrices over an arbitrary field with blocks of full rank

This note describes a technique for generating large non-singular matrices with blocks of full rank. Our motivation to construct such matrices arises in the white-box implementation of cryptographic algorithms with S-boxes.Comment:

Integrating Weakly Supervised Word Sense Disambiguation into Neural Machine Translation

This paper demonstrates that word sense disambiguation (WSD) can improve neural machine translation (NMT) by widening the source context considered when modeling the senses of potentially ambiguous words. We first introduce three adaptive clustering algorithms for WSD, based on k-means, Chinese restaurant processes, and random walks, which are then applied to large word contexts represented in a low-rank space and evaluated on SemEval shared-task data. We then learn word vectors jointly with sense vectors defined by our best WSD method, within a state-of-the-art NMT system. We show that the concatenation of these vectors, and the use of a sense selection mechanism based on the weighted average of sense vectors, outperforms several baselines including sense-aware ones. This is demonstrated by translation on five language pairs. The improvements are above one BLEU point over strong NMT baselines, +4% accuracy over all ambiguous nouns and verbs, or +20% when scored manually over several challenging words.Comment: To appear in TAC

A Survey of Access Control Models in Wireless Sensor Networks

Copyright 2014 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/)Wireless sensor networks (WSNs) have attracted considerable interest in the research community, because of their wide range of applications. However, due to the distributed nature of WSNs and their deployment in remote areas, these networks are vulnerable to numerous security threats that can adversely affect their proper functioning. Resource constraints in sensor nodes mean that security mechanisms with a large overhead of computation and communication are impractical to use in WSNs; security in sensor networks is, therefore, a challenge. Access control is a critical security service that offers the appropriate access privileges to legitimate users and prevents illegitimate users from unauthorized access. However, access control has not received much attention in the context of WSNs. This paper provides an overview of security threats and attacks, outlines the security requirements and presents a state-of-the-art survey on access control models, including a comparison and evaluation based on their characteristics in WSNs. Potential challenging issues for access control schemes in WSNs are also discussed.Peer reviewe

An evaluation of break-the-glass access control model for medical data in wireless sensor networks

Wireless Sensor Networks (WSNs) have recently attracted a lot of attention in the research community because it is easy to deploy them in the physical environment and collect and disseminate environmental data from them. The collected data from sensor nodes can vary based on what kind of application is used for WSNs. Data confidentiality and access control to that collected data are the most challenging issues in WSNs because the users are able to access data from the different location via ad-hoc manner. Access control is one of the critical requirements to prevent unauthorised access from users. The current access control models in information systems cannot be applied straightforwardly because of some limitations namely limited energy, resource and memory, and low computation capability. Based on the requirements of WSNs, we proposed the Break-The-Glass Access Control (BTG-AC) model which is the modified and redesigned version of Break-The-Glass Role-Based Access Control (BTG-RBAC) model. The several changes within the access control engine are made in BTG-RBAC to apply and fit in WSNs. We developed the BTG-AC model in Ponder2 package. Also a medical scenario was developed to evaluate the BTG-AC model for medical data in WSNs. In this paper, detail design, implementation phase, evaluation result and policies evaluation for the BTG-AC model are presented. Based on the evaluation result, the BTG-AC model can be used in WSNs after several modifications have been made under Ponder2 Package

First-passage theory of exciton population loss in single-walled carbon nanotubes reveals micron-scale intrinsic diffusion lengths

One-dimensional crystals have long range translational invariance which manifests as long exciton diffusion lengths, but such intrinsic properties are often obscured by environmental perturbations. We use a first-passage approach to model single-walled carbon nanotube (SWCNT) exciton dynamics (including exciton-exciton annihilation and end effects) and compare it to results from both continuous-wave and multi-pulse ultrafast excitation experiments to extract intrinsic SWCNT properties. Excitons in suspended SWCNTs experience macroscopic diffusion lengths, on the order of the SWCNT length, (1.3-4.7 um) in sharp contrast to encapsulated samples. For these pristine samples, our model reveals intrinsic lifetimes (350-750 ps), diffusion constants (130-350 cm^2/s), and absorption cross-sections (2.1-3.6 X 10^-17 cm^2/atom) among the highest previously reported.and diffusion lengths for SWCNTs.Comment: 6 pages, 3 figure