<p>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.</p><p>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.</p><p>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.</p><p>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>The reason for this study of the Swedish banking sector is that we suspect that collusion is at hand in the sector. We ground our suspiciousness on the extensive revenues and high retail banking fees. Swedish banking fees are the highest in EU. Based on this and that the banking sector is oligopolistic with only a few significant competitors we found it interesting to apply theories concerning tacit collusion on the banking sector. Our main conclusions are that cooperative pricing could be successful for banks since prices are a poor means of competition whereas customers focus on service quality instead of price. There is little asymmetry among the established banks and they cooperate through a number of systems. Since they cooperate through these systems the banks experience similar cost pressures and information is available. The Swedish bankers’ association plays an important role in the exchange of information. Thus, the facilitating features are strong and cooperative pricing can be profitable. An effective banking sector is essential for an economy and has a central role in the society as a whole. The presence of collusion can therefore have important implications, not only for the customers but also for the society. Efficiency costs also appear when collusion is at hand and can exceed the society’s welfare losses.</p>

The starting point in industrial organization is the notion of perfect competition. In a market with perfect competition, everything is transparent. In particular, there is perfect information about price, product value and firms' actions. This dissertation deals with exceptions from the world of perfect competition. The first two essays deal with imperfect information about prices and firms' actions, whereas the third essay considers imperfect information about the value of the traded goods. The first essay "Transparency and Competition" asks the question If prices are more or less transparent, does that favour consumers or producers? Starting from a search model, where some consumers know prices and other have to search, it is shown that a greater price transparency, i.e. a lower search cost, reduces the price in a single play of the game. When the game is repeated, however, the lower is the search cost, the easier it is to sustain collusion. Thus, promoting greater price transparency reduces the price in the stage game at the risk of increased opportunity for collusion. The second essay "Does Advertising Prevent Collusion?" analyses the case when firms can transmit price information to consumers by advertising. In contrast to the first essay, improved price transparency through advertising always reduces the price. It is even shown that the mere possibility of advertising can reduce the price, when firms are colluding. Thus, it is important to distinguish between advertising by firms and price publication by a third party. The first fosters competition, whereas thesecond may be harmful. In the third essay "Underwriter Competition" it is not the price that is more or less transparent. Instead, we consider a situation where sellers cannot transfer knowledge about their product values to the buyers. In order to overcome this problem, sellers may hire a renowned third party, an underwriter, who can certify that the products are of a certain value. The question that is posed in this essay is What happens if sellers can chose between different underwriters? It is shown that the underwriter market is a natural monopoly, where the underwriter with the highest ability toassess the value of the products gets the whole market. / Diss. Stockholm : Handelshögskolan, 2001

The reason for this study of the Swedish banking sector is that we suspect that collusion is at hand in the sector. We ground our suspiciousness on the extensive revenues and high retail banking fees. Swedish banking fees are the highest in EU. Based on this and that the banking sector is oligopolistic with only a few significant competitors we found it interesting to apply theories concerning tacit collusion on the banking sector. Our main conclusions are that cooperative pricing could be successful for banks since prices are a poor means of competition whereas customers focus on service quality instead of price. There is little asymmetry among the established banks and they cooperate through a number of systems. Since they cooperate through these systems the banks experience similar cost pressures and information is available. The Swedish bankers’ association plays an important role in the exchange of information. Thus, the facilitating features are strong and cooperative pricing can be profitable. An effective banking sector is essential for an economy and has a central role in the society as a whole. The presence of collusion can therefore have important implications, not only for the customers but also for the society. Efficiency costs also appear when collusion is at hand and can exceed the society’s welfare losses.

Många människor har efter avslutad psykoterapi tankar om densamma. Kanske fanns det ämnen som inte kom att benämnas, eller om de överhuvudtaget benämndes kom att göra det i begränsad utsträckning. Uppsatsen bygger dels på en empiriskt genomförd undersökning och dels på litteraturstudier. Det är en kvalitativ studie med halvstrukturerade frågor och meningskoncentrering. Fem personer har intervjuats, minst sex månader har gått sedan psykoterapin avslutades. Syftet med studien är att undersöka de processer som utifrån ett patientperspektiv ligger bakom att visst material inte aktualiserats i psykoterapin. För att göra intervjumaterialet överskådligt delades det upp i två dimensioner. Den första dimensionen beskriver de faktorer som förorsakat den förändrade upplevelsen av terapin. Den andra dimensionen beskriver de processer som hindrar att viktigt material aktualiseras. Dessa hinder handlar dels om specifika hinder som har med den psykoterapeutiska relationen att göra och dels handlar det om hinder som har att göra med olika försvarsstrategier som patienten använt sig av under sin psykoterapi. Flera av personerna uttryckte efter avslutad terapi en besvikelse över att man i psykoterapin upplevde en brist på djup och att det var ämnen som man ibland undvikit att prata om. Det framkom att problem i samband med överföringen innebar svåra motstånd mot fördjupningen av psykoterapin. En viktig slutsats i studien var att man antingen tenderade att skuldbelägga sig själv för de svårigheter som uppstod i psykoterapin alternativt att man lade över huvudansvaret för svårigheterna på terapeuten. Skam var ett återkommande ämne i flera av intervjuerna. Hur arbetsalliansen fungerade visade sig vara helt avgörande för hur psykoterapin utvecklades.

This work deals with legal aspects of collective dominant position under Article 82 of the Treaty establishing European Community (hereinafter- EC). The purpose is to reveal a legal definition and main features of collective dominant position. The author examines features and criteria which are established in the jurisprudence of EC institutions. The author examines features and criteria which are established in the jurisprudence of EC institutions. The author also indicates that the criteria for establishing collective dominance are not fully scrutinized under EC competition law. Moreover, the practice of EC institutions is analyzed not only under Article 82, which prohibits abuse of a dominant position, but also under Merger regulation to that extent which is necessary to reveal the main topic. Further the work presents problems which are found under these two institutions of EC competition law.

凱蘿‧邱琪兒在《醋湯姆》和《頂尖女孩》主要運用社會女性主義的觀點，探討女性在資本主義與父權的宰制下所遭受的壓迫。兩部作品中不但關注女性在社會上的地位，更重視在不同的社會階級下，女性會因階級上的差異而自我分化。 第二章在分析《醋湯姆》 中，邊緣弱勢女性在面對父權壓迫時的種種煎熬、憤怒、 與掙扎。《醋湯姆》以十七世紀基督徒獵殺女巫事件為背景，劇中被指控為女巫者，大多為社會邊緣人。其中指控他人為女巫者，竟也不乏女性，他們為了自我的利益和生存，願與父權共謀，欺壓弱勢階級，但自身也受父權機制的壓制。此外，本劇穿插的歌曲將十七世紀迫害女巫的厭女思想連結到二十世紀持續詆毀女性的態度。 第三章則著重《頂尖女孩》，雖然劇中出現諸位歷史上的成功女性，但至今女性仍 為了追求成功而缺乏團結甚至放棄母職。1980年代柴契爾主義（Thatcherism）的「成功女性」可以跨越階級的藩籬並獲取職場上的成就。但劇中批評Marlene，這種為了事業成功而放棄家庭的女性，不過是複製了另一種父權思維而已。另外，第三章也探討邱琪兒創新的寫作手法，她認為向父權屈從的女性角色在性別扮演上皆有其目的。女性角色過度強調外在的服裝藉此討好男性支配者，並展現自已的社會地位。例如，Marlene刻意穿著女性服裝遮掩自身，實際上是在遵從父權體制。 第四章為總結，邱琪兒在兩部劇本中指出部分的女性不願意團結，也拒絕幫助大多數的女性尋求轉變。藉由這兩部作品邱琪兒檢視女性間的階級衝突：女性為了自身利益和成就壓迫其他女性；遭受壓迫的女性因難以離開困境而敵對成功的女性。那些屈服於父權的女性不單強化了父權體制，更對處於不利地位的女性造就更加無望的未來。 / This study of Vinegar Tom and Top Girls demonstrates how Caryl Churchill asserts her socialist feminist concerns of intertwining class and gender issues. Both plays reveal the relationships between economic situation and gender oppression. She makes explicit that the class hierarchy plays a significant role in determining women’s experiences. The power and injustice are practiced by patriarchy and capitalism which uphold the oppression for women. The main concern of both plays is the indictment of the women in powerful class who participate in the patriarchal system. In Vinegar Tom, the witch accusations result from the patriarchal and class prejudice against poor and marginalized women. The power and interdependence of patriarchy and capitalism is manifested by some women who are patriarchal agents to victimize the women of lower class. In addition, by using the songs, Churchill presents shocking connection between medieval misogynist attitudes to witches and people’s continuing denigrating attitudes to women in general. Top Girls manifests, in spite of the historical women’s success, lack of solidarity and abandonment of motherhood remain unchanged in the present time. Thatcherite politics promoted the image of the high-flying female achiever who was capable of transcending class boundaries and of attaining material success in the work place. However, in this play, the successful woman, Marlene is a believer of patriarchy in disguise of a woman who forsakes her origins and family. In addition, there is a theme of performed gender roles in both plays. The women who collude with patriarchy focus on their dressing to achieve the practical purpose. In both plays, Churchill addresses the women who do not build solidarity or foster change for the majority of women. The women of upper class oppress the other women to attain their achievements or pursue their own benefit. The women of lower class cannot escape the plight and they are hostile to those upper class women’s advances. The women’s collusion with patriarchy strengthens the stable of the patriarchal system and causes a bleaker environment for those disadvantaged women.

Ce travail de recherche s’attache à spécifier la valeur argumentative de l’analogie à la lumière des recherches récentes sur l’analogie en prenant compte l’apport des sciences cognitives. Les liens de l’analogie avec une théorie plus générale de l’argumentation sont étudiés. Un corpus a été constitué, constituant une étude de cas, celui du discours de la critique cinématographique. Ce travail met en évidence le lien argumentatif entre analogie et connivence, phénomène qui a pu être observé dans diverses de ses manifestations et qui conduit à définir ce discours comme genre de discours dans la relation particulière qu’il instaure entre orateur et auditoire, entre critique et lecteur. Cette recherche a évolué vers ce qui semble être la caractéristique majeure de ce type de critiques : la recherche d'une forme ou d'une autre de connivence avec le lecteur. / This research aims to specify the argumentative value of analogy in light of recent research on analogy and its links with a more general theory of argumentation. A body has been formed, constituting a case study, the discourse of film criticism. This work highlights the argumentative relationship between analogy and collusion, a phenomenon that has been observed in a variety of its manifestations and leads to define this discourse as a kind of speech in the special relationship that develops between speaker and audience, between critical and reader. This research has evolved into what appears to be the major feature of this type of criticism: the search for a form or other of complicity with the reader.

This paper considers the widely successful employee discount pricing (EDP) promotional program of 2005 to uncover the nature of competition in the US automobile industry, with a specific focus on the big three automakers. In contrast to previous research on automobile competition, this paper uses quarterly average dealer-level transaction price data to capture the short term nature of inter-firm competition that might be embedded in such promotional programs. In doing so, a structural oligopoly model of differentiated products is setup explicitly incorporating the nature of competitive interactions. Results imply that the overall nature of competitiveness in the US automobile industry is consistent with a static model of Bertrand behaviour without any changes in conduct among the big three during the EDP promotion period. These results corroborate the problems of inventory backlog faced by the big three in recent years and indicate that the EDP program has been more of a novel marketing intent on part of the big three to clear up such backlogs.

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.