No / The FIRE trust and reputation model is a de-centralized trust model that can be applied for trust management in unstructured Peer-to-Peer (P2P) overlays. The FIRE model does not, however, consider malicious activity and possible collusive behavior in nodes of network and it is therefore susceptible to collusion attacks. This investigation reveals that FIRE is vulnerable to lying and cheating attacks and presents a trust management approach to detect collusion in direct and witness interactions among nodes based on colluding node's history of interactions. A witness ratings based graph building approach is utilized to determine possibly collusive behavior among nodes. Furthermore, various interaction policies are defined to detect and prevent collaborative behavior in colluding nodes. Finally a multidimensional trust model FIRE+ is devised for avoiding collusion attacks in direct and witness based interactions. The credibility of the proposed trust management scheme as an enhancement of the FIRE trust model is verified by extensive simulation experiments.

The present study evaluated the efficacy of a four-week seminar which emphasized the principles of Agentive Theory. This theory, which is compatible with theories of a phenomenological/ existential perspective, was first developed by C. T. Warner, an American philosopher. Agentive Theorists/Therapists emphasize that our negative emotions, ie., depression, anger, etc. , are assertions or judgments we make and not merely feelings we are responsible for controlling or expressing. Forty-eight outpatients who sought help with personal/emotional problems from a department of behavioral medicine were assigned to either a treatment or waiting-list control Group. Following a four-week treatment phase, the treatment group was shown to have made significantly greater improvement than the waiting-list control group with respect to general mental health, somatization, depression, anxiety, hostility, phobic anxiety, psychoticism, anger, and guilt.

An ever-increasing number of Internet applications, such as content and software distribution, distance learning, multimedia streaming, teleconferencing, and collaborative workspaces, need efficient and secure multicast communication. However, efficiency and security are competing requirements and balancing them to meet the application needs is still an open issue. In this thesis we study the efficiency versus security requirements tradeoffs in group key management for multicast communication. The efficiency is in terms of minimizing the group rekeying cost and the key storage cost, while security is in terms of achieving backward secrecy, forward secrecy, and resistance to collusion. We propose two new group key management schemes that balance the efficiency versus resistance to collusion. The first scheme is a flexible category-based scheme, and addresses applications where a user categorization can be done based on the user accessibility to the multicast channel. As shown by the evaluation, this scheme has a low rekeying cost and a low key storage cost for the controller, but, in certain cases, it requires a high key storage cost for the users. In an extension to the basic scheme we alleviate this latter problem. For applications where the user categorization is not feasible, we devise a cluster-based group key management. In this scheme the resistance to collusion is measured by an integer parameter. The communication and the storage requirements for the controller depend on this parameter too, and they decrease as the resistance to collusion is relaxed. The results of the analytical evaluation show that our scheme allows a fine-tuning of security versus efficiency requirements at runtime, which is not possible with the previous group key management schemes. / <p>Report code: LiU-TEK-LIC-2003:53.</p>

No description available.

The number of mobile applications (i.e., apps) is rapidly growing, as the mobile computing becomes an integral part of the modern user experience. Malicious apps have infiltrated open marketplaces for mobile platforms. These malicious apps can exfiltrate user's private data, abuse of system resources, or disrupting regular services. Despite the recent advances on mobile security, the problem of detecting vulnerable and malicious mobile apps with high detection accuracy remains an open problem. In this thesis, we address the problem of Android security by presenting a new quantitative program analysis framework for security vetting of Android apps. We first introduce a highly accurate proactive detection solution for detecting individual malicious apps. Our approach enforces benign property as opposed of chasing malware signatures, and uses one complex feature rather than multi-feature as in the existing malware detection methods. In particular, we statically extract a data-flow feature on how user inputs trigger sensitive critical operations, a property referred to as the user-trigger dependence. This feature is extracted through nontrivial Android-specific static program analysis, which can be used in various quantitative analytical methods. Our evaluation on thousands of malicious apps and free popular apps gives a detection accuracy (2% false negative rate and false positive rate) that is better than, or at least competitive against, the state-of-the-art. Furthermore, our method discovers new malicious apps available in the Google Play store that have not been previously detected by anti-virus scanning tools. Second, we present a new app collusion detection approach and algorithms to analyze pairs or groups of communicating apps. App collusion is a new technique utilized by the attackers to evade standard detection. It is a new threat where two or more apps, appearing benign, communicate to perform malicious task. Most of the existing solutions assume the attack model of a stand-alone malicious app, and hence cannot detect app collusion. We first demonstrate experimental evidence on the technical challenges associated with detecting app collusion. Then, we address these challenges by introducing a scalable and an in-depth cross-app static flow analysis approach to identify the risk level associated with communicating apps. Our approach statically analyzes the sensitivity and the context of each inter-app communication with low analysis complexity, and defines fine-grained security policies for the inter-app communication risk detection. Our evaluation results on thousands of free popular apps indicate that our technique is effective. It generates four times fewer false positives compared to the state-of-the-art collusion-detection solution, enhancing the detection capability. The advantages of our inter-app communication analysis approach are the analysis scalability with low complexity, and the substantially improved detection accuracy compared to the state-of-the-art solution. These types of proactive defenses solutions allow defenders to stay proactive when defending against constantly evolving malware threats. / Ph. D.

Après une introduction générale et un survey de littérature, l’apport de cette thèse est d’établir un lien entre le marché des biens et le marché de travail et de proposer un système légal optimal pour dissuader les comportements opportunistes au sein de l’entreprise. Tout au long de la thèse, le cadre d’analyse utilisé est le cas d’un monopole qui produit deux types de biens. Les consommateurs sont hétérogènes selon leurs préférences à la qualité. Le chapitre 2 analyse différentes structures d’agence afin de déterminer la meilleure structure qui permet à la fois de maximiser le profit de l’entreprise et de maximiser le bien-être des consommateurs et des employés. Le chapitre 3 examine la distorsion de la qualité des biens et du niveau d’effort des employés en asymétrie d’information avec sélection adverse sur le marché des biens et le marché de travail par rapport à l’information parfaite. Le chapitre 4 étend le chapitre 3 en étudiant la même problématique avec un problème d’aléa-moral sur le marché de travail en présence d’une collusion entre le superviseur et l’employé. Ce chapitre questionne le rôle du consommateur et du juge à dissuader cette forme de comportement opportuniste. / After a general introduction and a survey of literature, the contribution of this thesis is to establish a link between the goods market and the labor market and to propose optimal legal system to deter opportunistic behavior within the company. Throughout the thesis, we consider a monopoly that produces two types of good. Consumers are heterogeneous according to their preferences to quality. Chapter 2 analyzes different agency structures to determine the best structure that allows both to maximize the profit of the company and maximize the welfare of consumers and employees. Chapter 3 examines distortion of the quality of goods and the level of the workers’ effort with adverse selection on the goods market and the labor market compared with perfect information. This chapter examines the role of the consumer and the judge to discourage this kind of opportunistic behavior.Keywords: Quality of goods, quality of labor, optimal contract, portfolio of contract, opportunism, collusion, social welfare, optimal sanctions, firm design, law and economics.

Ma thèse intitulée “Gouvernance d'entreprise et concurrence sur le marché des produits” est composée de trois chapitres théoriques relevant essentiellement de l'Économie Industrielle. L'objectif principal est d'étudier comment le marché des produits interagit à la fois avec l'intérêt des parties prenantes lorsque l'information est parfaite et avec les incitations managériales (statiques et dynamiques) lorsque l'information est imparfaite.Le premier chapitre porte sur les interactions entre le mode de concurrence sur le marché des produits (Cournot vs. Bertrand) et les relations (conflictuelles ou conciliantes) entre les principaux acteurs (actionnaires, consommateurs et employés) lorsque l'intérêt des consommateurs est pris en compte dans la fonction objectif de la firme. Nous considérons un duopole symétrique où les firmes négocient préalablement avec les syndicats sur le salaire versé aux employés et puis se concurrencent entre elles sur le marché des biens. Nous montrons que l'orientation client (mesurée par le degré de prise en compte du surplus des consommateurs) peut inverser la hiérarchie traditionnelle entre les équilibres de Cournot et les équilibres de Bertrand. Une concurrence en prix (par rapport à une concurrence en quantité) est à même d'atténuer les conflits entre les actionnaires et les consommateurs et entre les actionnaires et les employés.Le deuxième chapitre examine comment les incitations managériales pourraient interagir avec la concurrence sur le marché des produits dans un contexte de sélection adverse et d'aléa moral. Nous considérons un oligopole de Cournot composé de n firmes identiques dont le coût marginal initial est une information privée du manager. L'effort du manager, qui est non observable, réduit indirectement le coût marginal initial. Dans un tel contexte, nous montrons qu'à l'optimum les paiements incitatifs versés aux managers ne sont pas nécessairement influencés par la concurrence sur le marché des produits.Le troisième chapitre étudie comment le contrat optimal entre l'actionnaire et le manager (résolution d'aléa moral répété) peut influencer la stabilité d'un cartel. Nous considérons un cartel composé de deux firmes identiques et dans chaque firme un actionnaire neutre à l'égard du risque offre un menu de contrats à un manager averse au risque. L'effort du manager influence le coût marginal de la firme (comme au chapitre 2) à chaque période. Nous montrons que, contrairement au cas où l'information est parfaite, le degré d'aversion au risque du manager n'impacte pas la stabilité du cartel lorsque le contrat optimal à long terme est mis en place. Le contrat optimal résout le problème d'aléa moral répété et limite également le pouvoir discrétionnaire du manager sur la décision de conduite du marché (collusion, déviation, ou compétition). / My thesis entitled « Corporate governance and product market competition : three essays » is a theoretical research in industrial organization. The primary objective is to investigate how product market (competition or collusion) interacts with the top-level design of corporate governance, which concerns specifically the stakeholders' relationships and managerial incentives (static and dynamic) under imperfect information. It is mainly based on three chapters dealing with different subtopics of this theme.The first chapter examines how social concern and product market competition (Cournot vs. Bertrand) may influence the relationships (conflicting or conciliating) between main stakeholders (shareholders, consumers and employees). We consider two identical firms, both taking care of the interests of consumers in their objective functions and allowing their employees' wages be negotiated with labor unions. We show that social concern may reverse the traditional ranking between Cournot and Bertrand equilibria. Our model also shows that price competition (compared to quantity competition) can to some extent attenuate the shareholders' conflicts with both consumers and employees.The second chapter investigates how managerial incentive payment under both adverse selection and moral hazard might interact with product market competition. We consider a Cournot oligopoly market consisting of n identical managerial firms, of which the initial marginal cost is the manager's private information and his unobservable effort indirectly reduces the initial level of marginal cost. We show with this setting that the optimal incentive payment solving informational problems is not necessarily influenced by product market competition.The third chapter studies how the optimal contract between shareholder and manager (solving repeated moral hazard) may influence the stability of a cartel. We consider a cartel consisting of two identical firms, within each a risk neutral shareholder offers a menu of contracts to a risk-averse manager who may shirk in each period. The manager's unobservable effort influences the firm's marginal cost (as in chapter 2). We show in contrary with the benchmark case (under perfect information) that the degree of risk-aversion plays no longer a role upon the stability of collusion: when the managerial compensation is independent of gross profit, the implementation of the optimal long-term contract solves repeated moral hazard but also constrains the manager's discretion over the decision of market conduct (collusion, deviation, or competition).

Secure multi-party computation (secure MPC) has been established as the de facto paradigm for protecting privacy in distributed computation. One of the earliest secure MPC primitives is the Shamir's secret sharing (SSS) scheme. SSS has many advantages over other popular secure MPC primitives like garbled circuits (GC) -- it provides information-theoretic security guarantee, requires no complex long-integer operations, and often leads to more efficient protocols. Nonetheless, SSS receives less attention in the signal processing community because SSS requires a larger number of honest participants, making it prone to collusion attacks. In this dissertation, I propose an agent-based computing framework using SSS to protect privacy in distributed signal processing. There are three main contributions to this dissertation. First, the proposed computing framework is shown to be significantly more efficient than GC. Second, a novel game-theoretical framework is proposed to analyze different types of collusion attacks. Third, using the proposed game-theoretical framework, specific mechanism designs are developed to deter collusion attacks in a fully distributed manner. Specifically, for a collusion attack with known detectors, I analyze it as games between secret owners and show that the attack can be effectively deterred by an explicit retaliation mechanism. For a general attack without detectors, I expand the scope of the game to include the computing agents and provide deterrence through deceptive collusion requests. The correctness and privacy of the protocols are proved under a covert adversarial model. Our experimental results demonstrate the efficiency of SSS-based protocols and the validity of our mechanism design.

Sue-and-settle is the name applied to a federal agency’s use of litigation to create policy outside of the normal regulatory process. This paper discusses the impact that the sue-and-settle policy has had on Congress, the judiciary, and the Environmental Protection Agency. Specifically, this paper will discuss the issues caused by the perception of collusion within the sue-and-settle policy. First, this paper examines whether a relationship occurs between the litigants. The paper then discusses whether the relationship between the litigants in sue-and-settle cases tends to be collusive or not. The second part of the paper examines how Congress, the Environmental Protection Agency, and the judiciary are viewed because of the continued perception of collusion in the agency’s settlements. Overall, this paper finds that, the impacts of the sue-and-settle policy, and the perception of collusion, has affected Congress, the Environmental Protection Agency, and the judiciary by increasing regulation, distorting the purpose of the courts, and resulting in a lost value for the regulatory process.

Par sa même nature, publicité est une caractéristique(fonction) pénétrante de vie économique. C'est un outil de plus en plus important dans des interactions stratégiques dans des marchés concurrentiels. Si le rôle de publicité doit améliorer(augmenter) l'image du produit dans les yeux de consommateurs et changer leurs préférences, ou les informer de la sortie d'un nouveau produit au marché, ou plutôt fournir des informations sur des prix ou les qualités de produits existants, une question importante rend perplexe les économistes : Pourquoi les consommateurs répondent-ils à la publicité ? Comme les économistes ont lutté avec cette question, trois vues ont apparu. La première vue est cette publicité est persuasif, c'est-à-dire il change les goût des consommateurs et crée la différenciation de produit fausse et la fidélité à la marque. En conséquence, il n'a aucune valeur "réelle"("vraie") aux consommateurs, mais incite plutôt la différenciation de produit artificielle. La deuxième vue est cette publicité est informatif. Selon cette approche, beaucoup de marchés sont caractérisés par des informations grand public imparfaites, puisque les coûts de recherche peuvent dissuader un consommateur d'apprendre de l'existence de chaque produit, le prix et la qualité. La publicité est la réponse endogène que le marché offre comme une solution : quand une société fait de la publicité, les consommateurs reçoivent des informations. La troisième vue est cette publicité est complémentaire au produit fait de la publicité. Selon cette perspective, publicité ne change pas les préférences des consommateurs, comme dans la vue persuasive; en outre, il, mais n'a pas besoin de pouvoir fournir des informations. Au lieu de cela, il est assumé que les consommateurs possèdent un jeu stable de préférences dans lesquelles la publicité entre directement dans une mode qui est complémentaire avec la consommation du produit fait de la publicité