Decentralised Communication in Autonomous Agent Swarms

Communication and information diffusion are typically difficult in situations where centralised structures may become unavailable. In this context, decentralised communication based on epidemic broadcast becomes essential. It can be seen as an opportunity-based flooding for message broadcasting within a swarm of autonomous agents, where each entity tries to share the information it possesses with its neighbours. As an example of applications for such a system, we present simulation results where agents have to coordinate to map an unknown area.

Impact of mobility constraints on epidemic broadcast mechanisms in delay-tolerant networks

In this paper, we investigate the effect of mobility constraints on epidemic broadcast mechanisms in DTNs (Delay-Tolerant Networks). Major factors affecting epidemic broadcast performances are its forwarding algorithm and node mobility. The impact of forwarding algorithm and node mobility on epidemic broadcast mechanisms has been actively studied in the literature, but those studies generally use unconstrained mobility models. The objective of this paper is therefore to quantitatively investigate the effect of mobility constraints on epidemic broadcast mechanisms. We evaluate the performances of three classes of epidemic broadcast mechanisms - P-BCAST (PUSH-based BroadCast), SA-BCAST (Self-Adaptive BroadCast), and HP-BCAST (History-based P-BCAST) - with a random waypoint mobility model with mobility constraints. Our finding includes that the existence of mobility constraints significantly improves the reach ability and dissemination speed of epidemic broadcast mechanisms while degrading their efficiency.

Angular dependence of the response of the nanoDot OSLD system for measurements at depth in clinical megavoltage beams

Purpose The purpose of this investigation was to assess the angular dependence of a commercial optically stimulated luminescence dosimeter (OSLD) dosimetry system in MV x-ray beams at depths beyondd max and to find ways to mitigate this dependence for measurements in phantoms. Methods Two special holders were designed which allow a dosimeter to be rotated around the center of its sensitive volume. The dosimeter's sensitive volume is a disk, 5 mm in diameter and 0.2 mm thick. The first holder rotates the disk in the traditional way. It positions the disk perpendicular to the beam (gantry pointing to the floor) in the initial position (0°). When the holder is rotated the angle of the disk towards the beam increases until the disk is parallel with the beam (“edge on,” 90°). This is referred to as Setup 1. The second holder offers a new, alternative measurement position. It positions the disk parallel to the beam for all angles while rotating around its center (Setup 2). Measurements with five to ten dosimeters per point were carried out for 6 MV at 3 and 10 cm depth. Monte Carlo simulations using GEANT4 were performed to simulate the response of the active detector material for several angles. Detector and housing were simulated in detail based on microCT data and communications with the manufacturer. Various material compositions and an all-water geometry were considered. Results For the traditional Setup 1 the response of the OSLD dropped on average by 1.4% ± 0.7% (measurement) and 2.1% ± 0.3% (Monte Carlo simulation) for the 90° orientation compared to 0°. Monte Carlo simulations also showed a strong dependence of the effect on the composition of the sensitive layer. Assuming the layer to completely consist of the active material (Al2O3) results in a 7% drop in response for 90° compared to 0°. Assuming the layer to be completely water, results in a flat response within the simulation uncertainty of about 1%. For the new Setup 2, measurements and Monte Carlo simulations found the angular dependence of the dosimeter to be below 1% and within the measurement uncertainty. Conclusions The dosimeter system exhibits a small angular dependence of approximately 2% which needs to be considered for measurements involving other than normal incident beams angles. This applies in particular to clinicalin vivo measurements where the orientation of the dosimeter is dictated by clinical circumstances and cannot be optimized as otherwise suggested here. When measuring in a phantom, the proposed new setup should be considered. It changes the orientation of the dosimeter so that a coplanar beam arrangement always hits the disk shaped detector material from the thin side and thereby reduces the angular dependence of the response to within the measurement uncertainty of about 1%. This improvement makes the dosimeter more attractive for clinical measurements with multiple coplanar beams in phantoms, as the overall measurement uncertainty is reduced. Similarly, phantom based postal audits can transition from the traditional TLD to the more accurate and convenient OSLD.

The role of digital screens in urban life: New opportunities for placemaking

Large digital screens are becoming prevalent across today’s cities dispersing into everyday urban spaces such as public squares and cultural precincts. Examples, such as Federation Square, demonstrate the opportunities for using digital screens to create a sense of place and to add long-term social, cultural and economic value for citizens, who live and work in those precincts. However, the challenge of implementing digital screens in new urban developments is to ensure they respond appropriately to the physical and sociocultural environment in which they are placed. Considering the increasing rate at which digital screens are being embedded into public spaces, it is surprising that the programs running on these screens still seem to be stuck in the cinematic model. The availability of advanced networking and interaction technologies offers opportunities for information access that goes beyond free-to-air television and advertising. This chapter revisits the history and current state of digital screens in urban life and discusses a series of research studies that involve digital screens as interface between citizens and the city. Instead of focusing on technological concerns, the chapter presents a holistic analysis of these studies, with the aim to move towards a more comprehensive understanding of the sociocultural potential of this new media platform, and how the digital content is linked with the spatial quality of the physical space, as well as the place and role of digital screens within the smart city movement.

Submission to the draft Migration Assurance Policy - Improving the transition to the fixed-line national broadband network review

The rights of individuals to self-determination and participation in social, political and economic life are recognised and supported by Articles 1, 3 and 25 of the International Covenant on Civil and Political Rights 1966.4 Article 1 of the United Nations’ Human Rights Council’s Resolution on the Promotion and Protection of Human Rights on the Internet of July 2012 confirms individuals have the same rights online as offline. Access to the internet is essential and as such the UN: Calls upon all States to promote and facilitate access to the Internet and international cooperation aimed at the development of media and information and communications facilities in all countries (Article 3) Accordingly, access to the internet per se is a fundamental human right, which requires direct State recognition and support.5 The obligations of the State to ensure its citizens are able, and are enabled, to access the internet, are not matters that should be delegated to commercial parties. Quite simply – access to the internet, and high-speed broadband, by whatever means are “essential services” and therefore “should be treated as any other utility service”...

An analysis of TLS handshake proxying

Content delivery networks (CDNs) are an essential component of modern website infrastructures: edge servers located closer to users cache content, increasing robustness and capacity while decreasing latency. However, this situation becomes complicated for HTTPS content that is to be delivered using the Transport Layer Security (TLS) protocol: the edge server must be able to carry out TLS handshakes for the cached domain. Most commercial CDNs require that the domain owner give their certificate's private key to the CDN's edge server or abandon caching of HTTPS content entirely. We examine the security and performance of a recently commercialized delegation technique in which the domain owner retains possession of their private key and splits the TLS state machine geographically with the edge server using a private key proxy service. This allows the domain owner to limit the amount of trust given to the edge server while maintaining the benefits of CDN caching. On the performance front, we find that latency is slightly worse compared to the insecure approach, but still significantly better than the domain owner serving the content directly. On the security front, we enumerate the security goals for TLS handshake proxying and identify a subtle difference between the security of RSA key transport and signed-Diffie--Hellman in TLS handshake proxying; we also discuss timing side channel resistance of the key server and the effect of TLS session resumption.

A cryptographic analysis of the TLS 1.3 handshake protocol candidates

The Internet Engineering Task Force (IETF) is currently developing the next version of the Transport Layer Security (TLS) protocol, version 1.3. The transparency of this standardization process allows comprehensive cryptographic analysis of the protocols prior to adoption, whereas previous TLS versions have been scrutinized in the cryptographic literature only after standardization. This is even more important as there are two related, yet slightly different, candidates in discussion for TLS 1.3, called draft-ietf-tls-tls13-05 and draft-ietf-tls-tls13-dh-based. We give a cryptographic analysis of the primary ephemeral Diffie–Hellman-based handshake protocol, which authenticates parties and establishes encryption keys, of both TLS 1.3 candidates. We show that both candidate handshakes achieve the main goal of providing secure authenticated key exchange according to an augmented multi-stage version of the Bellare–Rogaway model. Such a multi-stage approach is convenient for analyzing the design of the candidates, as they establish multiple session keys during the exchange. An important step in our analysis is to consider compositional security guarantees. We show that, since our multi-stage key exchange security notion is composable with arbitrary symmetric-key protocols, the use of session keys in the record layer protocol is safe. Moreover, since we can view the abbreviated TLS resumption procedure also as a symmetric-key protocol, our compositional analysis allows us to directly conclude security of the combined handshake with session resumption. We include a discussion on several design characteristics of the TLS 1.3 drafts based on the observations in our analysis.

The role of professional identity & self-interest in career choices in the emerging ICT workforce

The influence of professional identity and self-interest on the educational and career choices of the emerging Information and Communications Technology (ICT) workforce is considered in this thesis. Interviews were conducted with 52 ICT students from four Australian tertiary education institutions and the findings indicated that professional identity and self-interest should be considered together, rather than separately, to understand career decisions in relation to the ICT industry. Professional identity is associated with the accrual of symbolic resources including status and esteem, mastery, sense of belonging and attachment. By contrast, self-interest is associated with the perceived likelihood of the accrual of material (economic and social) resources.

Teachers working in an online world

This book brings together a number of academics who have conducted research and written about effective practices and pedagogies that incorporate the use of information and communications technologies (ICT). The book is intended for graduate and undergraduate students in Teacher Education programmes, as well as teachers and those who areinterested in contemporary educational issues. The authors in this book have been engaged in rethinking education with ICT. Implicit in this, is the view that we need to reconceptualise our pedagogies and practices in order to make schools relevant to the lives of the young people who inhabit them. The chapters in this book are based on empirically grounded research work. The chapters illustrate the various dimensions of innovative practices with ICT that can extend teachers’ pedagogies and engage learners so that they are able to extend their potential for knowledge building in new and dynamic ways.

Adding value: Principals’ perceptions of the role of the teacher-librarian

This paper reports on a study into principals’ perceptions of the role of the teacher-librarian. Nine principals in Australia were interviewed about the role of the teacher-librarian and library in their school. The findings indicated a range of ways in which the teacher-librarian adds value to the school, including in their role as teacher, providing the principal with a broad perspective on the workings of the school, providing advice and ideas, and providing leadership in the use of information and communications technology (ICT) at the school. It also identified a number of personal qualities valued by principals.