Katrina Falkner

Engineering Security into Distributed Systems: A Survey of Methodologies

Rapid technological advances in recent years have precipitated a general shift towards software distribution as a central computing paradigm. This has been accompanied by a corresponding increase in the dangers of security breaches, often causing security attributes to become an inhibiting factor for use and adoption. Despite the acknowledged importance of security, especially in the context of open and collaborative environments, there is a growing gap in the survey literature relating to systematic approaches (methodologies) for engineering secure distributed systems. In this paper, we attempt to fill the aforementioned gap by surveying and critically analyzing the state-of-the-art in security methodologies based on some form of abstract modeling (i.e. model-based methodologies) for, or applicable to, distributed systems. Our detailed reviews can be seen as a step towards increasing awareness and appreciation of a range of methodologies, allowing researchers and industry stakeholders to gain a comprehensive view of the field and make informed decisions. Following the comprehensive survey we propose a number of criteria reflecting the characteristics security methodologies should possess to be adopted in real-life industry scenarios, and evaluate each methodology accordingly. Our results highlight a number of areas for improvement, help to qualify adoption risks, and indicate future research directions.

Developing authentic problem solving skills in introductory computing classes

The ability to solve problems is the key to developing software, and it is an ability that can be difficult to learn. Introductory Computer Science students are often taught syntax and semantics, along with simple problems designed to develop logical, structured thinking, but authentic problem-solving skills are rarely developed at these early stages. In this paper we describe an approach to introductory computer science education that addresses student engagement through integrating cooperative learning techniques and authentic problem solving processes throughout each aspect of the curriculum. Over a period of 4 years, the introductory computer science course at the University of Adelaide has been modified to support a cooperative learning style. A three-stage methodology has been implemented in place of traditional lectures to achieve this. The process focuses on observing the application of programming techniques, observing problem solving techniques and then applying cooperative problem solving exercises in the classroom. The results from this change in teaching methodology have been an increase in attendance rates at lectures and practical sessions as well as improved learning outcomes as measured by exam results. Student experience surveys show students have greater motivation for learning and believe they have a better understanding of concepts since the changes have occurred.

Collaborative learning and anxiety: a phenomenographic study of collaborative learning activities

Collaborative learning encourages deeper learning, producing significant benefit in learning outcomes. There has been an increasing trend to adopt collaborative activities, due to the expected learning benefits but also because of the expected social benefits and their impact on transition concerns. However, collaborative activities may also introduce additional stress and anxiety for students as they cope with altered participation expectations, and the need to develop collaboration, communication and management skills concurrently with their discipline skills. In this paper we describe a phenomenographic analysis of students reflections on collaborative activities, including their perceptions of the purpose of such activities, and corresponding behaviours.

Scalable Surveillance Software Architecture

Video surveillance is a key technology for enhanced protection of facilities such as airports and power stations from various types of threat. Networks of thousands of IP-based cameras are now possible, but current surveillance methodologies become increasingly ineffective as the number of cameras grows. Constructing software that efficiently and reliably deals with networks of this size is a distributed information processing problem as much as it is a video interpretation challenge. This paper demonstrates a software architecture approach to the construction of large scale surveillance network software and explores the implications for instantiating surveillance algorithms at such a scale. A novel architecture for video surveillance is presented, and its efficacy demonstrated through application to an important class of surveillance algorithms.

Supporting and structuring “contributing student pedagogy” in Computer Science curricula

Contributing student pedagogy (CSP) builds upon social constructivist and community-based learning principles to create engaging and productive learning experiences. What makes CSP different from other, related, learning approaches is that it involves students both learning from and also explicitly valuing the contributions of other students. The creation of such a learning community builds upon established educational psychology that encourages deep learning, reflection and engagement. Our school has recently completed a review and update of its curriculum, incorporating student content-creation and collaboration into the design of key courses across the curriculum. Our experiences, based on several years of experimentation and development, support CSP-based curriculum design to reinforce the value of the student perspective, the clear description of their own transformative pathway to knowledge and the importance of establishing student-to-student networks in which students are active and willing participants. In this paper, we discuss the tools and approaches that we have employed to guide, support and structure student collaboration across a range of courses and year levels. By providing an account of our intentions, our approaches and tools, we hope to provide useful and transferrable knowledge that can be readily used by other academics who are considering this approach.

Increasing the effectiveness of automated assessment by increasing marking granularity and feedback units

Computer-based assessment is a useful tool for handling large-scale classes and is extensively used in the automated assessment of student programming assignments in Computer Science. The forms that this assessment takes, however, can vary widely from simple acknowledgement to a detailed analysis of output, structure and code. This study focusses on output analysis of submitted student assignment code and the degree to which changes in automated feedback influence student marks and persistence in submission. Data was collected over a four year period, over 22 courses but we focus on one course for this paper. Assignments were grouped by the number of different units of automated feedback that were delivered per assignment to investigate if students changed their submission behaviour or performance as the possible set of marks, that a student could achieve, changed. We discovered that pre-deadline results improved as the number of feedback units increase and that post-deadline activity was also improved as more feedback units were available.

Amplifying side channels through performance degradation

Interference between processes executing on shared hardware can be used to mount performance-degradation attacks. However, in most cases, such attacks offer little benefit for the adversary. In this paper, we demonstrate that software-based performance-degradation attacks can be used to amplify side-channel leaks, enabling the adversary to increase both the amount and the quality of information captured. We identify a new information leak in the OpenSSL implementation of the ECDSA digital signature algorithm, albeit seemingly unexploitable due to the limited granularity of previous trace procurement techniques. To overcome this imposing hurdle, we combine the information leak with a microarchitectural performance-degradation attack that can slow victims down by a factor of over 150. We demonstrate how this combination enables the amplification of a side-channel sufficiently to exploit this new information leak. Using the combined attack, an adversary can break a private key of the secp256k1 curve, used in the Bitcoin protocol, after observing only 6 signatures---a four-fold improvement over all previously described attacks.

Identifying computer science self-regulated learning strategies

Computer Science students struggle to develop fundamental programming skills and software development processes. Crucial to successful mastery is the development of discipline specific cognitive and metacognitive skills, including self-regulation. We can assist our students in the process of reflection and self-regulation by identifying and articulating successful self-regulated learning strategies for specific discipline contexts. However, in order to do so, we must develop an understanding of those discipline-specific strategies that are successful and can be readily adopted by students. In this paper, we analyse student reflections from an introductory software development course, identifying the usage of self-regulated learning strategies that are either specific to the software development domain, or articulated in that context. This study assists in the understanding of how Computer Science students develop learning skill within the discipline, and provides examples to guide the development of scaffolding activities to assist learning development.

Estimating camera overlap in large and growing networks

Large-scale intelligent video surveillance requires an accurate estimate of the relationships between the fields of view of the cameras in the network. The exclusion approach is the only method currently capable of performing online estimation of camera overlap for networks of more than 100 cameras, and implementations have demonstrated the capability to support networks of 1000 cameras. However, these implementations include a centralised processing component, with the practical result that the resources (in particular, memory) of the central processor limit the size of the network that can be supported. In this paper, we describe a new, partitioned, implementation of exclusion, suitable for deployment to a cluster of commodity servers. Results for this implementation demonstrate support for significantly larger camera networks than was previously feasible. Furthermore, the nature of the partitioning scheme enables incremental extension of system capacity through the addition of more servers, without interrupting the existing system. Finally, formulae for requirements of system memory and bandwidth resources, verified by experimental results, are derived to assist engineers seeking to implement the technique.

Integrating communication skills into the computer science curriculum

Computer Science majors must be able to communicate effectively. Industry surveys identify the development of communication and critical thinking skills as key to the reform of the higher education sector. However, academics are challenged by time and discipline content pressures, as well as a lack of familiarity with the teaching and assessment of communication skills content. There is considerable existing work in the area of communication skills development, positioned both in terms of curriculum guidelines for effective communication skills development, and example communication skills activities. However, this research is deficient in detailed, contextualised methodologies and frameworks for the development of communication skills within the Computer Science curriculum. We present a new methodology, building upon well established theoretical frameworks, designed to assist academics in the development of communication skills activities integrated with discipline content across the curriculum. We illustrate this methodology in the design of a CS1/CS2 communication skills course.