Termination-insensitive noninterference leaks more than just a bit

Current tools for analysing information flow in programs build upon ideas going back to Denning's work from the 70's. These systems enforce an imperfect notion of information flow which has become known as termination-insensitive noninterference. Under this version of noninterference, information leaks are permitted if they are transmitted purely by the program's termination behaviour (i.e., whether it terminates or not). This imperfection is the price to pay for having a security condition which is relatively liberal (e.g. allowing while-loops whose termination may depend on the value of a secret) and easy to check. But what is the price exactly? We argue that, in the presence of output, the price is higher than the “one bit” often claimed informally in the literature, and effectively such programs can leak all of their secrets. In this paper we develop a definition of termination-insensitive noninterference suitable for reasoning about programs with outputs. We show that the definition generalises “batch-job” style definitions from the literature and that it is indeed satisfied by a Denning-style program analysis with output. Although more than a bit of information can be leaked by programs satisfying this condition, we show that the best an attacker can do is a brute-force attack, which means that the attacker cannot reliably (in a technical sense) learn the secret in polynomial time in the size of the secret. If we further assume that secrets are uniformly distributed, we show that the advantage the attacker gains when guessing the secret after observing a polynomial amount of output is negligible in the size of the secret

Exploring efficacy in personal constraint negotiation: an ethnography of mountaineering tourists

Limited work has explored the relationship between efficacy and personal constraint negotiation for adventure tourists, yet efficacy is pivotal to successful activity participation as it influences people’s perceived ability to cope with constraints, and their decision to use negotiation strategies. This paper explores these themes with participants of a commercially organised mountaineering expedition. Phenomenology-based ethnography was adopted to appreciate the social and cultural mountaineering setting from an emic perspective. Ethnography is already being used to understand adventure participation, yet there is considerable scope to employ it further through researchers immersing themselves into the experience. The findings capture the interaction between the ethnographer and the group members, and provide an embodied account using their lived experiences. Findings reveal that personal mountaineering skills, personal fitness, altitude sickness and fatigue were the four key types of personal constraint. Self-efficacy, negotiation-efficacy and other factors, such as hardiness and motivation, influenced the effectiveness of negotiation strategies. Training, rest days, personal health, and positive self-talk were negotiation strategies. A conceptual model illustrates these results and demonstrates the interplay between efficacy and the personal constraint negotiation journey for led mountaineers

FliPpr: A Prettier Invertible Printing System

When implementing a programming language, we often write a parser and a pretty-printer. However, manually writing both programs is not only tedious but also error-prone; it may happen that a pretty-printed result is not correctly parsed. In this paper, we propose FliPpr, which is a program transformation system that uses program inversion to produce a CFG parser from a pretty-printer. This novel approach has the advantages of fine-grained control over pretty-printing, and easy reuse of existing efficient pretty-printer and parser implementations

Worker/wrapper/makes it/faster

Much research in program optimization has focused on formal approaches to correctness: proving that the meaning of programs is preserved by the optimisation. Paradoxically, there has been comparatively little work on formal approaches to efficiency: proving that the performance of optimized programs is actually improved. This paper addresses this problem for a general-purpose optimization technique, the worker/wrapper transformation. In particular, we use the call-by-need variant of improvement theory to establish conditions under which the worker/wrapper transformation is formally guaranteed to preserve or improve the time performance of programs in lazy languages such as Haskell

Vertical Carbon Nanotube Devices With Nanoscale Lengths Controlled Without Lithography

Vertical single-walled carbon nanotubes (vSWCNTs) are synthesized within highly ordered porous anodic alumina (PAA) templates supported on Si substrates. A process for obtaining thin-film PAA with long-range ordered nanopores is presented in this paper. Each nanopore contains at most one v-SWCNT that is supported by a dielectric and addressed by electrochemically formed Pd nanowire source contacts and evaporated Pd drain contacts. Characteristics of these completely vertical, two-terminal nanotube devices are presented. Control of the v-SWCNT length is demonstrated using a straightforward etching process with lengths of less than 100 nm achieved without the need for complex/expensive lithography. This effective nanoscale length control of highly ordered v-SWCNTs provides a practical basis for the realization of CNT-based nanoelectronics

Economic Potential of Greenhouse Gas Emission Reductions: Comparative Role for Soil Sequestration in Agriculture and Forestry

We use the Agricultural Sector Model to analyze the economic potential of soil carbon sequestration as one of several agricultural greenhouse gas emission mitigation strategies, including afforestation. For low incentives on carbon emission savings, agricultural soil carbon sequestration is the most cost-efficient strategy. As incentive levels increase above $50 per ton of carbon equivalent, afforestation and biofuel production become the key strategies, while the role of soil carbon diminishes. If saturating sinks are discounted based on their net present value, the competitive economic equilibrium among agricultural mitigation strategies shifts away from soil carbon sequestration and afforestation and toward more biofuel production. Regardless of the discounting assumption and the carbon savings incentive level, the economic potential of soil carbon sequestration never attains its technical potential as estimated by soil scientists. The study also estimates the impacts of agricultural mitigation policies on welfare, prices, production, and input use in the traditional food and fiber sector and the effects of emission leakage from unregulated agricultural sources

Mediating boundaries between knowledge and knowing: ICT and R4D praxis

Research for development (R4D) praxis (theory-informed practical action) can be underpinned by the use of Information and Communication Technologies (ICTs) which, it is claimed, provide opportunities for knowledge working and sharing. Such a framing implicitly or explicitly constructs a boundary around knowledge as reified, or commodified – or at least able to be stabilized for a period of time (first order knowledge). In contrast ‘third-generation knowledge’ emphasizes the social nature of learning and knowledge-making; this reframes knowledge as a negotiated social practice, thus constructing a different system boundary. This paper offers critical reflections on the use of a wiki as a data repository and mediating technical platform as part of innovating in R4D praxis. A sustainable social learning process was sought that fostered an emergent community of practice among biophysical and social researchers acting for the first time as R4D co-researchers. Over time the technologically mediated element of the learning system was judged to have failed. This inquiry asks: How can learning system design cultivate learning opportunities and respond to learning challenges in an online environment to support R4D practice? Confining critical reflection to the online learning experience alone ignores the wider context in which knowledge work took place; therefore the institutional setting is also considered

Spontaneous cerebellar hemorrhage in a patient taking apixaban

AbstractObjectivesAtrial fibrillation is closely associated with cardioembolic stroke. Until recently, warfarin has been the gold standard for the treatment of atrial fibrillation. Since 2010 the United States Food and Drug Administration has approved three new agents for anticoagulation in patients with atrial fibrillation. The purpose of this case report is to discuss some of the practical implications for using these agents.MethodsA patient taking apixaban presented with a spontaneous cerebellar hemorrhage. While the patient was initially considered a candidate for surgical intervention, the lack of literature addressing surgical intervention in patients on novel anticoagulation clouded the clinical decision-making. The patient was ultimately managed with administration of activated prothrombin complex concentrate, blood pressure control, frequent clinical assessments and airway protection. The patient did not undergo craniotomy for hematoma evacuation.ConclusionsRecent FDA approval of several novel oral anticoagulants for use in patients with atrial fibrillation has resulted in a significant number of patients formerly treated with warfarin being switched to these newer agents. There remains a lack of clear guidelines for the management of hemorrhagic complications. This case report describes one management strategy and highlights the paucity of current evidence to support critical clinical decisions