Malleability attacks on multi-party key agreement protocols

Multi-party key agreement protocols indirectly assume that each principal equally contributes to the final form of the key. In this paper we consider three malleability attacks on multi-party key agreement protocols. The first attack, called strong key control allows a dishonest principal (or a group of principals) to fix the key to a pre-set value. The second attack is weak key control in which the key is still random, but the set from which the key is drawn is much smaller than expected. The third attack is named selective key control in which a dishonest principal (or a group of dishonest principals) is able to remove a contribution of honest principals to the group key. The paper discusses the above three attacks on several key agreement protocols, including DH (Diffie-Hellman), BD (Burmester-Desmedt) and JV (Just-Vaudenay). We show that dishonest principals in all three protocols can weakly control the key, and the only protocol which does not allow for strong key control is the DH protocol. The BD and JV protocols permit to modify the group key by any pair of neighboring principals. This modification remains undetected by honest principals.

Multi-stage collapse events in the South Soufrière Hills, Montserrat as recorded in marine sediment cores

We present new evidence for sector collapses of the South Soufrière Hills (SSH) edifice, Montserrat during the mid-Pleistocene. High-resolution geophysical data provide evidence for sector collapse, producing an approximately 1 km3 submarine collapse deposit to the south of SSH. Sedimentological and geochemical analyses of submarine deposits sampled by sediment cores suggest that they were formed by large multi-stage flank failures of the subaerial SSH edifice into the sea. This work identifies two distinct geochemical suites within the SSH succession on the basis of trace-element and Pb-isotope compositions. Volcaniclastic turbidites in the cores preserve these chemically heterogeneous rock suites. However, the subaerial chemostratigraphy is reversed within the submarine sediment cores. Sedimentological analysis suggests that the edifice failures produced high-concentration turbidites and that the collapses occurred in multiple stages, with an interval of at least 2 ka between the first and second failure. Detailed field and petrographical observations, coupled with SEM image analysis, shows that the SSH volcanic products preserve a complex record of magmatic activity. This activity consisted of episodic explosive eruptions of andesitic pumice, probably triggered by mafic magmatic pulses and followed by eruptions of poorly vesiculated basaltic scoria, and basaltic lava flows.

On secure multi-party computation in black-box groups

We study the natural problem of secure n-party computation (in the passive, computationally unbounded attack model) of the n-product function f G (x 1,...,x n ) = x 1 ·x 2 ⋯ x n in an arbitrary finite group (G,·), where the input of party P i is x i  ∈ G for i = 1,...,n. For flexibility, we are interested in protocols for f G which require only black-box access to the group G (i.e. the only computations performed by players in the protocol are a group operation, a group inverse, or sampling a uniformly random group element). Our results are as follows. First, on the negative side, we show that if (G,·) is non-abelian and n ≥ 4, then no ⌈n/2⌉-private protocol for computing f G exists. Second, on the positive side, we initiate an approach for construction of black-box protocols for f G based on k-of-k threshold secret sharing schemes, which are efficiently implementable over any black-box group G. We reduce the problem of constructing such protocols to a combinatorial colouring problem in planar graphs. We then give two constructions for such graph colourings. Our first colouring construction gives a protocol with optimal collusion resistance t < n/2, but has exponential communication complexity O(n*2t+1^2/t) group elements (this construction easily extends to general adversary structures). Our second probabilistic colouring construction gives a protocol with (close to optimal) collusion resistance t < n/μ for a graph-related constant μ ≤ 2.948, and has efficient communication complexity O(n*t^2) group elements. Furthermore, we believe that our results can be improved by further study of the associated combinatorial problems.

Nonlinear Model Predictive Control for a multi-rotor with heavy slung load

In this paper a novel controller for stable and precise operation of multi-rotors with heavy slung loads is introduced. First, simplified equations of motions for the multi-rotor and slung load are derived. The model is then used to design a Nonlinear Model Predictive Controller (NMPC) that can manage the highly nonlinear dynamics whilst accounting for system constraints. The controller is shown to simultaneously track specified waypoints whilst actively damping large slung load oscillations. A Linear-quadratic regulator (LQR) controller is also derived, and control performance is compared in simulation. Results show the improved performance of the Nonlinear Model Predictive Control (NMPC) controller over a larger flight envelope, including aggressive maneuvers and large slung load displacements. Computational cost remains relatively small, amenable to practical implementation. Such systems for small Unmanned Aerial Vehicles (UAVs) may provide significant benefit to several applications in agriculture, law enforcement and construction.

Enhanced stochastic mobility prediction with multi-output Gaussian processes

Outdoor robots such as planetary rovers must be able to navigate safely and reliably in order to successfully perform missions in remote or hostile environments. Mobility prediction is critical to achieving this goal due to the inherent control uncertainty faced by robots traversing natural terrain. We propose a novel algorithm for stochastic mobility prediction based on multi-output Gaussian process regression. Our algorithm considers the correlation between heading and distance uncertainty and provides a predictive model that can easily be exploited by motion planning algorithms. We evaluate our method experimentally and report results from over 30 trials in a Mars-analogue environment that demonstrate the effectiveness of our method and illustrate the importance of mobility prediction in navigating challenging terrain.

Towards a multi-element simulation of heavily over-consolidated bagasse using a material subroutine

A better understanding of the behaviour of prepared cane and bagasse, and the ability to model the mechanical behaviour of bagasse as it is squeezed in a milling unit to extract juice, would help identify how to improve the current process. There are opportunities to decrease bagasse moisture from a milling unit. The behaviour of bagasse in chutes is poorly understood. Previous investigations have shown that juice flow through bagasse obeys Darcy’s permeability law, that the grip of the rough surface of the grooves on the bagasse can be represented by the Mohr-Coulomb failure criterion for soils, and that the internal mechanical behaviour of the bagasse is critical state behaviour similar to that for sand and clay. Progress has been made in the last 11 years towards implementing a mechanical model for bagasse in finite element software. The objective is to be able to correctly simulate various simple mechanical loading conditions measured in the laboratory. Combining these behaviours together is thought to have a high probability of reproducing the complicated stress conditions in a milling unit. This paper reports on progress made towards modelling the fifth and final (and most challenging) of the simple loading conditions: the shearing of heavily over-consolidated bagasse, using a specific model for bagasse in a multi-element simulation.

A multi-level ecological model of psychotropic prescribing to adults with intellectual disability

Purpose – Simple linear accounts of prescribing do not adequately address reasons “why” doctors prescribe psychotropic medication to people with intellectual disability (ID). Greater understanding of the complex array of factors that influence decisions to prescribe is needed. Design/methodology/approach – After consideration of a number of conceptual frameworks that have potential to better understand prescribing of psychotropic medication to adults with ID, an ecological model of prescribing was developed. A case study is used to outline how the model can provide greater understanding of prescribing processes. Findings – The model presented aims to consider the complexity and multi-dimensional nature of community-based psychotropic prescribing to adults with ID. The utility of the model is illustrated through a consideration of the case study. Research limitations/implications – The model presented is conceptual and is as yet untested. Practical implications – The model presented aims to capture the complexity and multi-dimensional nature of community-based psychotropic prescribing to adults with ID. The model may provide utility for clinicians and researchers as they seek clarification of prescribing decisions. Originality/value – The paper adds valuable insight into factors influencing psychotropic prescribing to adults with ID. The ecological model of prescribing extends traditional analysis that focuses on patient characteristics and introduces multi-level perspectives that may provide utility for clinicians and researchers.

Sibling bullying perpetration: Associations with gender, grade, peer perpetration, trait anger, and moral disengagement

This study investigated bullying amongst siblings in both traditional and cyber forms, and the associations of gender, grade, peer bullying perpetration, trait anger and moral disengagement. The participants were 455 children in grades 5 to 12 (262 girls and 177 boys with 16 unknown gender) who had a sibling. As the number of siblings who only bullied by technology was low, these associations were not able to be calculated. However, the findings showed that the percentage of sibling traditional bullying perpetration (31.6%) was higher than peer bullying perpetration (9.8%). Sibling bullies reported engaging in complex behaviours of perpetration and victimisation in both the physical and in cyber settings, although the number was small. Gender, trait anger, moral disengagement and bullying peers at school (but not grade) were all significantly associated with sibling traditional bullying perpetration. The implications of the findings are discussed for bullying intervention and prevention programs to understand childhood bullying in diverse contexts.

HFL micro inverter with front-end diode clamped multi-level inverter and half-wave cycloconverter

A high-frequency-link (HFL) micro inverter with a front-end diode clamped multi-level inverter and a grid-connected half-wave cycloconverter is proposed. The diode clamped multi-level inverter with an auxiliary capacitor is used to generate high-frequency (HF) three level quasi square-wave output and it is fed into a series resonant tank to obtain high frequency continuous sinusoidal current. The obtained continuous sinusoidal current is modulated by using the grid-connected half-wave cycloconverter to obtain grid synchronized output current in phase with the grid voltage. The phase shift power modulation is used with auxiliary capacitor at the front-end multi-level inverter to have soft-switching. The phase shift between the HFL resonant current and half-wave cycloconverter input voltage is modulated to obtain grid synchronized output current.

Space vector modulated cascade multi-level inverter for PMSG wind generation systems

Modulation and control of a cascade multilevel inverter, which has a high potential in future wind generation applications, are presented. The inverter is a combination of a high power, three level “bulk inverter” and a low power “conditioning inverter”. To minimize switching losses, the bulk inverter operates at a low frequency producing square wave outputs while high frequency conditioning inverter is used to suppress harmonic content produced by the bulk inverter output. This paper proposes an improved Space Vector Modulation (SVM) algorithm and a neutral point potential balancing technique for the inverter. Furthermore, a maximum power tracking controller for the Permanent Magnet Synchronous Generator (PMSG) is described in detail. The proposed SVM technique eliminates most of the computational burdens on the digital controller and renders a greater controllability under varying DC-link voltage conditions. The DC-link capacitor voltage balancing of both bulk and conditioning inverters is carried out using Redundant State Selection (RSS) method and is explained in detail. Experimental results are presented to verify the proposed modulation and control techniques.

Transmedia Storytelling: From Interviewing to Multi-Platform

There is nothing new under the sun – so the saying goes, and in a digital age of recording oral histories, this holds true. Despite advances and innovations across the board in information and communication technology in the field of oral history it is essentially only the devices we record on that have changed. However, what has emerged is a plethora of ways that oral history interviews can be used to produce multimedia, or transmedia storytelling outputs- for exhibitions in public institutions, schools and by communities to engage interested groups, and in families and by individuals wanting to play with new ways of telling their family stories and histories. In 2010, QUT’s Creative Industries introduced a postgraduate unit called Transmedia Storytelling: From Interviewing to Multi-Platform, which was the first postgraduate course of its kind in Australia. Based in a Creative Writing discipline, but open to all coursework Masters, PhD, Research Masters and Doctorate of Creative Industries students, this unit introduces students to the theory and practice of semi-structured interviewing techniques, oral history conventions and applications, and the art of storytelling across various platforms.

STAC living. Promoting efficient multi-residential buildings in subtropical climates.

STAC is a mobile application (app) designed to promote the benefits of climate-aware urban development in Subtropical environments. Although, STAC is primarily tool for understanding climate efficient buildings in Brisbane, Australia, it also demonstrates how other exemplary buildings operate in other subtropical cities of the world. The STAC research and development team applied research undertaken by the Centre for Subtropical Design (Brisbane) to profile buildings past and present that have contributed to the creation of a vibrant society, a viable economy, a healthy environment, and an authentic sense of place. In collaboration with researchers from the field of Interaction Design, this knowledge and data was collated, processed and curated for presentation via a custom mobile application designed to distribute this important research for review and consideration on-location in local settings and for comparison across all other global subtropical regions and projects identified by this research. This collaboration adopted a Design-based Research (DBR) Methodology guided by the main tenets of research and design iteration and cross-discipline collaboration in real-world settings, resulting in the formulation of contextually-sensitive design principles, theories, and tools for design intervention. Combined with significant context review of available technology and data and subsequent case study analysis of exemplar design applications.

Street reads - Creating mobile walking events

By 2012 mobile devices had become the main interface for people to access information about anything from their current GPS position to the latest book reviews. What was less accessible were tools and techniques for writers to leverage this new technology to construct and distribute located stories. This project began with a series of master classes for local Brisbane writers to demonstrate processes and techniques for imagining, constructing and distributing stories. Most significantly, this project equipped writers with how to identify and adopt various mobile services and applications to research, produce and deliver packaged multi-modal content for readers to access and experience stories in the very locations from which they were inspired. Four stories by four writers were selected to be developed and published as location-based events in four different neighbourhoods across Brisbane. These writers were mentored throughout the writing process and a model was developed for them to simply upload several multi-modal chapters for access on location by readers using QR codes. These activities culminated in a major 25 day event presented by Brisbane City Council and supported by Brisbane Writers Festival and Queensland Writers Centre. The 'Street Reads' event presented the four stories on location in Cannon Hill, Darra, Toowong and West End. The significance of the Street Reads project went beyond extending the capacity for writers to access mobile technologies as a new platform for distributing stories. This event also motivated readers to travel to neighbourhoods to experience them in ways that had not previously imagined possible. These located stories were fictionalisations of actual events and characters that have current and historic importance to these places. These histories are hidden from view and yet can provide locals and visitors with a new found appreciation for the past and set an example for how neighbourhoods can become active stages for the sharing of stories inspiring a deeper connection with each other and an agency for participating in the development of the identity of the local places they inhabit together. Due to the success of the project and by employing more advanced tools now available, Street reads has been further developed by Brisbane City Council and is now available as a the Story City App available for download at itunes.

Value management in design planning : a systems-based framework for multi-disciplinary team involvement

This thesis investigates the Value Management processes used by construction project clients that effects project team involvement in VM workshops during the design stage of the projects. It is based on five case studies of the Malaysian international airport construction project packages. The focus of the research is on how issues related to infrastructure design that can improve construction processes on-site are being identified, analysed and resolved through multi-disciplinary team participation. The degrees of interaction, diversity of visualisation aids, certain cultural dimensions and the system thinking approach are found to have significant influence in maximizing participation among project team members during the entire VM workshop process.

The influence of families on early adolescent school connectedness : evidence that this association varies with adolescent involvement in peer drinking networks

School connectedness is central to the long term well-being of adolescents, and high quality parent-child relationships facilitate school connectedness. This study examined the extent to which family relationship quality is associated with the school connectedness of pre- and early teenagers, and how this association varies with adolescent involvement in peer drinking networks. The sample consisted of 7,372 10-14 year olds recruited from 231 schools in 30 Australian communities. Participants completed the Communities that Care youth survey. A multi-level model of school connectedness was used, with a random term for school-level variation. Key independent variables included family relationship quality, peer drinking networks, and school grade. Control variables included child gender, sensation seeking, depression, child alcohol use, parent education, and language spoken at home. For grade 6 students, the association of family relationship quality and school connectedness was lower when peer drinking networks were present, and this effect was nonsignificant for older (grade 8) students. Post hoc analyses indicated that the effect for family relationship quality on school connectedness was nonsignificant when adolescents in grade 6 reported that the majority of friends consumed alcohol. The results point to the importance of familyschool partnerships in early intervention and prevention.