Cooperative Beamforming and User Selection for Improving the Security of Relay-aided Systems

A relay network in which a source wishes to convey a confidential message to a legitimate destination with the assistance of trusted relays is considered. In particular, cooperative beamforming and user selection techniques are applied to protect the confidential message. The secrecy rate (SR) and secrecy outage probability (SOP) of the network are investigated first, and a tight upper bound for the SR and an exact formula for the SOP are derived. Next, asymptotic approximations for the SR and SOP in the high signal-to-noise ratio (SNR) regime are derived for two different schemes: i) cooperative beamforming and ii) multiuser selection. Further, a new concept of cooperative diversity gain, namely, adapted cooperative diversity gain (ACDG), which can be used to evaluate security level of a cooperative relaying network, is investigated. It is shown that the ACDG of cooperative beamforming is equal to the conventional cooperative diversity gain of traditional multiple-input single-output networks, while the ACDG of the multiuser scenario is equal to that of traditional single-input multiple-output networks.

A Cyber-Physical Security Analysis of Synchronous-Islanded Microgrid Operation

Cyber-security research in the field of smart grids is often performed with a focus on either the power and control domain or the Information and Communications Technology (ICT) domain. The characteristics of the power equipment or ICT domain are commonly not collectively considered. This work provides an analysis of the physical effects of cyber-attacks on microgrids – a smart grid construct that allows continued power supply when disconnected from a main grid. Different types of microgrid operations are explained (connected, islanded and synchronous-islanding) and potential cyber-attacks and their physical effects are analyzed. A testbed that is based on physical power and ICT equipment is presented to validate the results in both the physical and ICT domain.

On the Security of Balanced Encoding Countermeasures

Most cryptographic devices should inevitably have a resistance against the threat of side channel attacks. For this, masking and hiding schemes have been proposed since 1999. The security validation of these countermeasures is an ongoing research topic, as a wider range of new and existing attack techniques are tested against these countermeasures. This paper examines the side channel security of the balanced encoding countermeasure, whose aim is to process the secret key-related data under a constant Hamming weight and/or Hamming distance leakage. Unlike previous works, we assume that the leakage model coefficients conform to a normal distribution, producing a model with closer fidelity to real-world implementations. We perform analysis on the balanced encoded PRINCE block cipher with simulated leakage model and also an implementation on an AVR board. We consider both standard correlation power analysis (CPA) and bit-wise CPA. We confirm the resistance of the countermeasure against standard CPA, however, we find with a bit-wise CPA that we can reveal the key with only a few thousands traces.

Twitter Sentiment Analysis for Security-Related Information Gathering

Analysing public sentiment about future events, such as demonstration or parades, may provide valuable information while estimating the level of disruption and disorder during these events. Social media, such as Twitter or Facebook, provides views and opinions of users related to any public topics. Consequently, sentiment analysis of social media content may be of interest to different public sector organisations, especially in the security and law enforcement sector. In this paper we present a lexicon-based approach to sentiment analysis of Twitter content. The algorithm performs normalisation of the sentiment in an effort to provide intensity of the sentiment rather than positive/negative label. Following this, we evaluate an evidence-based combining function that supports the classification process in cases when positive and negative words co-occur in a tweet. Finally, we illustrate a case study examining the relation between sentiment of twitter posts related to English Defence League and the level of disorder during the EDL related events.

The Impact of Multimedia Education on Uptake of Comprehensive Eye Examinations in Rural China: A Randomized, Controlled Trial

PURPOSE: To study the effect of multimedia education on acceptance of comprehensive eye examinations (CEEs), critical for detecting glaucoma and diabetic eye disease, among rural Chinese patients using a randomized, controlled design.
METHODS: Patients aged ≥40 years were recruited from 52 routine clinic sessions (26 intervention, 26 control) conducted at seven rural hospitals in Guangdong, China. Subjects answered demographic questionnaires, were tested on knowledge about CEEs and chronic eye disease, and were told the cost of examination (range US$0-8). At intervention sessions, subjects were cluster-randomized to view a 10-minute video on the value of CEEs and retested. Control subjects were not retested. Trial outcomes were acceptance of CEEs (primary outcome) and final knowledge scores (secondary outcome).
RESULTS: At baseline, >70% (p = 0.70) of both intervention (n = 241, 61.2 ± 12.3 years) and control (n = 218, 58.4 ± 11.7 years) subjects answered no knowledge questions correctly, but mean scores on the test (maximum 5 points) increased by 1.39 (standard deviation 0.12) points (p < 0.001) after viewing the video. Intervention (73.0%) and control (72.9%) subjects did not differ in acceptance of CEEs (p > 0.50). In mixed-effect logistic regression models, acceptance of CEEs was associated with availability of free CEEs (odds ratio 18.3, 95% confidence interval 1.32-253.0), but not group assignment or knowledge score. Acceptance was 97.5% (79/81) when free exams were offered.
CONCLUSIONS: Education increased knowledge about but not acceptance of CEEs, which was generally high. Making CEEs free could further increase acceptance.

Exploiting Direct Links for Physical Layer Security in Multi-User Multi-Relay Networks

We present two physical layer secure transmission schemes for multi-user multi-relay networks, where the communication from M users to the base station is assisted by direct links and by N decode-and-forward relays. In this network, we consider that a passive eavesdropper exists to overhear the transmitted information, which entails exploiting the advantages of both direct and relay links for physical layer security enhancement. To fulfill this requirement, we investigate two criteria for user and relay selection and examine the achievable secrecy performance. Criterion I performs a joint user and relay selection, while Criterion II performs separate user and relay selections, with a lower implementation complexity. We derive a tight lower bound on the secrecy outage probability for Criterion I and an accurate analytical expression for the secrecy outage probability for Criterion II. We further derive the asymptotic secrecy outage probabilities at high transmit signal-to-noise ratios and high main-to-eavesdropper ratios for both criteria. We demonstrate that the secrecy diversity order is min (MN, M + N) for Criterion I, and N for Criterion II. Finally, we present numerical and simulation results to validate the proposed analysis, and show the occurrence condition of the secrecy outage probability floor

The supporting role of emerging multimedia technologies in higher education

In this paper we give an overview of current investigations into the incorporation of cutting edge technologies within the Higher Education teaching domain. In particular, the role of audio is discussed through a number of case studies. The paper then concludes with a discussion of the authors' plans to incorporate audio and video content as supplementary course material for a technical undergraduate module

A construção da identidade em ambientes digitais: estudo de caso sobre a construção da identidade online no Sapo Campus e em ambientes informais

O reconhecimento da dimensão criativa, participativa e social da rede trouxe profundas alterações à forma como se percebem e compreendem as questões relacionadas com a identidade, a educação, a prática e o conhecimento. Num cenário caraterizado pela conectividade e pela facilidade de acesso a pessoas e conteúdos, a rede oferece aos indivíduos um espaço onde podem interagir, trabalhar na sua aprendizagem, trocar experiências e construir uma identidade e reputação acessíveis a toda a comunidade. Quando se torna praticamente impossível permanecer fora do mundo digital e, consequentemente, da produção de uma identidade online (Costa e Torres, 2011; Warburton, 2009), a presença construída pelo indivíduo na rede surge como um currículo vitae ativo e dinâmico, revelador não apenas das competências adquiridas e certificadas em contextos de aprendizagem formais como daquelas desenvolvidas pela interação com os pares, pela partilha e pela comunicação. Partindo da análise da utilização de uma plataforma suportada institucionalmente (i.e. SAPO Campus), o presente trabalho de investigação tem como principal objetivo a análise e caraterização da construção da identidade online de um grupo de alunos do Mestrado em Comunicação Multimédia da Universidade de Aveiro num espaço providenciado pela instituição de ensino que frequentam. Com recurso a inquéritos por questionário, entrevistas em profundidade (realizadas aos participantes no estudo e a profissionais da área da comunicação e gestão de carreiras) e observação direta (análise quantitativa e qualitativa dos conteúdos publicados pelos participantes no SAPO Campus e em duas redes informais), procurou-se ainda caraterizar e analisar a identidade construída em espaços formais e informais, e aferir a importância – para alunos, instituição e mercado – da identidade online enquanto espaço de manifestação e divulgação de competências. Ainda que circunscrita ao contexto específico do Mestrado em Comunicação Multimédia e mais especificamente aos alunos cuja identidade online foi objeto de estudo, análise dos dados permite avançar que, de facto, os alunos estão conscientes da sua própria identidade online bem como da relevância de construir uma identidade e reputação sólidas e autênticas, que reflitam as suas competências e capacidades enquanto aprendentes e profissionais. Assim, poder-se-á avançar que no SAPO Campus os alunos estão a construir uma identidade online mais formal e cuidada, editando e selecionando os conteúdos de acordo com o contexto. Neste espaço, a maioria das publicações está diretamente relacionada com os trabalhos de investigação dos participantes, que recorrem à sua partilha nas redes informais para aumentar a visibilidade e exposição dos conteúdos publicados. Os participantes no estudo revelaram ainda valorizar o sentimento de segurança providenciado pelas tecnologias institucionais, bem como a possibilidade de construir uma identidade numa plataforma associada à sua instituição de ensino. Do estudo efetuado resultou ainda uma proposta de um modelo para a análise da identidade online, que poderá ser utilizado na análise da presença dos indivíduos em ambientes online formais e informais. Apresentando a identidade online como uma realidade assente na representação digital, na gestão da privacidade e na reputação construída na rede, o modelo foi aplicado aos dados recolhidos pelo estudo, conduzindo ao desenho de duas grandes formas de estar na rede: identidade orientada pelo contexto, e identidade orientada pelo utilizador. Quando as caraterísticas dos mundos digitais alteram a forma de produção da identidade e num cenário onde a contextualização de dados e informação assume uma importância crescente, este estudo de caso poderá contribuir para o conhecimento dos processos de construção da identidade em espaços formais e informais, da forma como os indivíduos gerem e constroem a sua identidade online, e ainda sobre a importância e o impacto da construção de uma identidade online consciente e credível para a reputação dos indivíduos e das Instituições de Ensino Superior.