Complexity and Unwinding for Intransitive Noninterference

The paper considers several definitions of information flow security for intransitive policies from the point of view of the complexity of verifying whether a finite-state system is secure. The results are as follows. Checking (i) P-security (Goguen and Meseguer), (ii) IP-security (Haigh and Young), and (iii) TA-security (van der Meyden) are all in PTIME, while checking TO-security (van der Meyden) is undecidable, as is checking ITO-security (van der Meyden). The most important ingredients in the proofs of the PTIME upper bounds are new characterizations of the respective security notions, which also lead to new unwinding proof techniques that are shown to be sound and complete for these notions of security, and enable the algorithms to return simple counter-examples demonstrating insecurity. Our results for IP-security improve a previous doubly exponential bound of Hadj-Alouane et al

Information Security as Strategic (In)effectivity

Security of information flow is commonly understood as preventing any information leakage, regardless of how grave or harmless consequences the leakage can have. In this work, we suggest that information security is not a goal in itself, but rather a means of preventing potential attackers from compromising the correct behavior of the system. To formalize this, we first show how two information flows can be compared by looking at the adversary's ability to harm the system. Then, we propose that the information flow in a system is effectively information-secure if it does not allow for more harm than its idealized variant based on the classical notion of noninterference

A Framework of Socioeconomic Organisation: Redefining Original Institutional Economics Along Critical Realist Philosophical Lines

The paper develops a theoretical framework of socioeconomic organisation to enrich understanding of the complex interrelation between economy and institutional environment. To achieve this, key elements from both new and old institutional economics are combined and integrated under the philosophical platform of critical realism. Institutionalist research can be, and has been, informed by a range of philosophical positions and analytical standpoints. Critical realism, in turn, has certain advantages, over the other philosophical perspectives, in discussing the institutional organisation of urban socioeconomy. These mainly stem from its ontological arguments that allow the dissociation of institutional structure from human agency, and acknowledge the separate identity and causal powers of institutions without undermining their agent-dependent nature. This is important because it enables a neat identification and analysis of the institutional qualities, mechanisms, causal powers and relations that characterise the socioeconomic fabric. Moreover, the fact that the realist ontology is compatible with a variety of economic theories renders its fusion with institutionalism on the whole both valid and feasible. The paper starts delineating the philosophical tenets of critical realism, which provide the basis for the development of a stratified ontological framework discussing the institutional organisation of the urban socioeconomy. In particular, a three-layer, interlocked reality is identified describing the complexity, multidimensionality, and dynamic character of the socioeconomic world. It is argued that deeper tendencies, capacities, ‘instincts’ and qualities of the human essence (understood as ‘creativity’, ‘emulation’ and ‘culture’) condition the institutional environment (differentiated in economic, political, legal, and social terms), which in turn constitutes the terrain upon which organisational arrangements are manifested and socioeconomic events are actualised. In these terms, institutions are defined as ingrained regularities or established rules of human life that mould and determine agents’ perception, expectations and behaviour, providing order, stability and certainty in social interaction and economic organisation. The paper closes summarising the epistemological and methodological position espoused to establish a generic analytical framework that can be used to investigate the institutional texture of the urban/regional socioeconomic environment.

Deterioration and Noise in Technologies of Audio Reproduction

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Towards Scalable Measures of Quality of Interaction: Motor Interference

© 2019 Copyright held by the owner/author(s).Motor resonance, the activation of an observer's motor control system by another actor's movements, has been claimed to be an indicator for quality of interaction. Motor interference as one of the consequences of the presence of resonance can be detected by analysing an actor's spatial movements. It has therefore been used as an indicator for the presence of motor resonance. Unfortunately, the experimental paradigm in which motor interference has been shown to be detectable is ecologically implausible both in terms of the types of movements employed and the number of repetitions required. In the presented experiment we tested whether some of these experimental constraints can be relaxed or modified towards a more naturalistic behaviour without losing the ability to detect the interference effect. In the literature, spatial variance has been analytically quantified in many different ways. This study found these analytical variations to be nonequivalent by implementing them. Back-and-forth transitive movements were tested for motor interference; the effect was found to be more robust than with left-right movements, though the direction of interference was opposite to that reported in the literature. We conclude that motor interference, when measured by spatial variation, lacks promise for embedding in naturalistic interaction scenarios because the effect sizes were small.Peer reviewe

Semantic indeterminacy in object relative clauses

This article examined whether semantic indeterminacy plays a role in comprehension of complex structures such as object relative clauses. Study 1 used a gated sentence completion task to assess which alternative interpretations are dominant as the relative clause unfolds; Study 2 compared reading times in object relative clauses containing different animacy configurations to unambiguous passive controls; and Study 3 related completion data and reading data. The results showed that comprehension difficulty was modulated by animacy configuration and voice (active vs. passive). These differences were well correlated with the availability of alternative interpretations as the relative clause unfolds, as revealed by the completion data. In contrast to approaches arguing that comprehension difficulty stems from syntactic complexity, these results suggest that semantic indeterminacy is a major source of comprehension difficulty in object relative clauses. Results are consistent with constraint-based approaches to ambiguity resolution and bring new insights into previously identified sources of difficulty. (C) 2007 Elsevier Inc. All rights reserved

Many-to-Many Information Flow Policies

Information flow techniques typically classify information according to suitable security levels and enforce policies that are based on binary relations between individual levels, e.g., stating that information is allowed to flow from one level to another. We argue that some information flow properties of interest naturally require coordination patterns that involve sets of security levels rather than individual levels: some secret information could be safely disclosed to a set of confidential channels of incomparable security levels, with individual leaks considered instead illegal; a group of competing agencies might agree to disclose their secrets, with individual disclosures being undesired, etc. Motivated by this we propose a simple language for expressing information flow policies where the usual admitted flow relation between individual security levels is replaced by a relation between sets of security levels, thus allowing to capture coordinated flows of information. The flow of information is expressed in terms of causal dependencies and the satisfaction of a policy is defined with respect to an event structure that is assumed to capture the causal structure of system computations. We suggest applications to secret exchange protocols, program security and security architectures, and discuss the relation to classic notions of information flow control