Security of multi-agent systems: A case study on comparison shopping

The multi-agent-systems paradigm is becoming more and more popular as a basis for realizing net-based solutions. This development is accompanied by an increasing relevance of security issues. For instance, the potential loss of privacy and other assets is a major concern for, both merchants and customers, in Internet-based commerce and, without being properly addressed, such very legitimate concerns hamper the growth of e-commerce.This article uses a comparison-shopping scenario to introduce a general methodology for formally verifying the security of multi-agent systems. Following the approach of possibilistic information flow security, the flow of information between and within agents is restricted in order to ensure that secrets will not be disclosed to unauthorized meddlers. The security requirements for the overall system are then decomposed into requirements for the individual agents that can be verified independently from each other. Exploiting the modular structure of a multi-agent system considerably reduces the complexity of the overall security analysis. The techniques for decomposing security requirements, for verifying individual agents, and for deriving global security guarantees for the entire system from locally verified properties are all generic in the sense that they apply also to many other systems and security requirements than the ones that appear in the example scenario.     

Mindestanforderungen für Prognosegutachten1

Die aus Richtern am Bundesgerichtshof, Bundesanw?lten, forensischen Psychiatern und Psychologen, Sexualmedizinern und weiteren Juristen bestehende interdisziplin?re Arbeitsgruppe, die sich bereits mit Mindestanforderungen für Schuldf?higkeitsgutachten befasst hat², hat nun auch die nachfolgenden Empfehlungen für die vielf?ltig zu erstattenden forensischen Prognosegutachten erarbeitet. Wegen der H?ufigkeit und der Bedeutung dieser Gutachten in der Strafvollstreckung ist die Arbeitsgruppe um drei erfahrene Vollstreckungsrichter erweitert worden. Die Mitglieder waren: VRinBGH Dr. Rissing-van Saan, VRiBGH Nack, RiBGH Basdorf, RiBGH Dr. Bode, RiBGH Dr. Boetticher, RiBGH Maatz, RiBGH Pfister, VRiBGH a.D. Dr. Sch?fer, die Bundesanw?lte Hannich und Altvater, die Vollstreckungsrichter RiOLG B?hm, Karlsruhe, RiOLG Dr. Müller-Metz, Frankfurt a.M., VRiLG Dr. Wolf, Marburg, der Kriminologe Prof. Dr. Sch?ch, München, der Rechtsanwalt Dr. Deckers, Düsseldorf, die forensischen Psychiater Prof. Dr. Berner, Hamburg, Prof. Dr. Dittmann, Basel, Prof. Dr. Kr?ber, Berlin, Prof. Dr. Leygraf, Essen, Dr. Müller-Isberner, Gie?en, Prof. Dr. Nedopil, München, Prof. Dr. Sa?, Aachen, Dr. Habermeyer, Rostock, die Sexualmediziner Prof. Dr. Dr. Beier, Berlin, Prof. Dr. Bosinski, Kiel, und der Rechtspsychologe Prof. Dr. K?hnken, Kiel. ¹ Dieser Beitrag ist bereits erschienen in NStZ 26:237–544 (2006), Abdruck mit freundlicher Genehmigung des Verlages C. H. Beck ² NStZ 25:57–62 (2005), Nervenarzt 76:1154–1159 (2005), Forens Psychiatr Psychol Kriminol 1:3–9 (2007)     

Statistical power analyses using G<Superscript>*</Superscript>Power 3.1: Tests for correlation and regression analyses

G^*Power is a free power analysis program for a variety of statistical tests. We present extensions and improvements of the version introduced by Faul, Erdfelder, Lang, and Buchner (2007) in the domain of correlation and regression analyses. In the new version, we have added procedures to analyze the power of tests based on (1) single-sample tetrachoric correlations, (2) comparisons of dependent correlations, (3) bivariate linear regression, (4) multiple linear regression based on the random predictor model, (5) logistic regression, and (6) Poisson regression. We describe these new features and provide a brief introduction to their scope and handling.     

Simultaneous learning of different regularities in sequence learning tasks: limits and characteristics

Two experiments are reported which were designed to investigate the generality and the power of the mechanisms underlying sequence learning. In both experiments, participants reacted to systematic sequences of tones. They were informed that there was a tone systematicity. Participants were not told that the interval between a response to a tone and the onset of the subsequent tone (response-signal interval, RSI) also varied according to a fixed regularity. Experiment 1 showed that the unattended RSIs were learned when they were uniquely related to the tone sequence, but not when the relation was ambiguous. Experiment 2 showed that, on the basis of the traditional reaction time performance measure, participants who learned the RSIs by attending to their systematicity could not be distinguished from those in an incidental learning condition in which the RSI systematicity was unattended. However, a model-based analysis of the processes contributing to judgements about the event sequences suggested that the two groups had acquired qualitatively different knowledge. Received: 3 March 2000 / Accepted: 2 November 2000     

Recall-to-reject: The effect of category cues on false recognition

Four experiments examined the effect of category cueing on recall-to-reject, one of the central memory-editing mechanisms thought to prevent the occurrence of false memories. When category names were used as retrieval cues, the typically observed false recognition effect was eliminated for semantically associated distractors (Experiment 1a) and, moreover, a reduction in the absolute level of the false alarm rate was found for phonologically associated distractors (Experiment 2a). In addition to the old/new-recognition data, analyses using multinomial models support the interpretation that category cueing was successful in increasing the probability of recall-to-reject (Experiments 1b and 2b). The results are in line with dual-process theories of recognition memory and provide further evidence for recall-to-reject in single item recognition. They demonstrate its potential to reduce false recognition even when explicit instructions are not given. In addition, the results demonstrate that the paradigm can give rise to side effects that oppose recall-to-reject. A simultaneous familiarity increase can explain why many studies failed to find evidence for recall-to-reject in terms of false alarm rates.     

Your life in snapshots: Mobile weblogs

Nicola Döring and Alex Gundolf's article on the development of 'moblogs' or mobile weblogs allows us to approach recent mobile phone industry developments from an academic standpoint. Pointing to the convergence of mobile and Internet technology, 'moblogs' provide a means for users to archive their lives via photos that can be taken via a mobile phone and viewed via the Internet. Nokia have named their product to provide this service 'lifeblog', and it is this uncensored publication of everyday life that Döring and Gundolf investigate, from subjects as mundane as a user capturing his waking state everyday, to as personally and globally historic as the moblog by a US soldier in Iraq. What we are seeing in the 'moblog' is how organically some product development is in the mobile world--the early moblogging software came not from operators, handset or software manufacturers but from the social software community that thrives on the Internet. It is precisely this level of organic, spontaneous product development that occurs as a by-product of networked communities that many companies seek and often fail to emulate.     

Effects of spatial response coding on distractor processing: Evidence from auditory spatial negative priming tasks with keypress,joystick, and head movement responses

Attention, Perception, & Psychophysics - Prior studies of spatial negative priming indicate that distractor-assigned keypress responses are inhibited as part of visual, but not auditory,...