Individual Security and Network Design with Malicious Nodes

Networks are beneficial to those being connected but can also be used as carriers of contagious hostile attacks. These attacks are often facilitated by exploiting corrupt network users. To protect against the attacks, users can resort to costly defense. The decentralized nature of such protection is known to be inefficient but the inefficiencies can be mitigated by a careful network design. Is network design still effective when not all users can be trusted? We propose a model of network design and defense with byzantine nodes to address this question. We study the optimal defended networks in the case of centralized defense and, for the case of decentralized defense, we show that the inefficiencies due to decentralization can be fully mitigated, despite the presence of the byzantine nodes.Comment: 19 pages, 3 figure

Swap Equilibria under Link and Vertex Destruction

We initiate the study of the destruction or adversary model (Kliemann 2010) using the swap equilibrium (SE) stability concept (Alon et al., 2010). The destruction model is a network formation game incorporating the robustness of a network under a more or less targeted attack. In addition to bringing in the SE concept, we extend the model from an attack on the edges to an attack on the vertices of the network. We prove structural results and linear upper bounds or super-linear lower bounds on the social cost of SE under different attack scenarios. For the case that the vertex to be destroyed is chosen uniformly at random from the set of max-sep vertices (i.e., where each causes a maximum number of separated player pairs), we show that there is no tree SE with only one max-sep vertex. We conjecture that there is no tree SE at all. On the other hand, we show that for the uniform measure, all SE are trees (unless two-connected). This opens a new research direction asking where the transition from “no cycle” to “at least one cycle” occurs when gradually concentrating the measure on the max-sep vertices

Games in Networks under Robustness, Locality, and Coloring Aspects

Decentralization is a key concept in modern networks, such as the Internet, social networks, or wireless phone or sensor networks. The systematic study of how networks are formed by a multitude of non-cooperative or only mildly cooperative players, is a vivid topic in Discrete Mathe- matics, Computer Science, and Economics. In 2010, a variant addressing robustness aspects was introduced. In this model, known as adversary model or destruction model, one link in the network is destroyed at random af- ter the network has been formed. Players anticipate this disruption and try to build a network that gives them good connectivity even after the destruction. How efficiently can this be done in a decentralized setting? This thesis advances our knowledge regarding the adversary model: we bring in the modern equilibrium concept of swap equilibrium and we extend to the destruction of one vertex. This disruption tends to be more severe compared to the case that just one link is destroyed. We characterize several settings, where for some, the formed networks are provably efficient, while for others, we show they can be inefficient up to a certain degree. Apart from the adversary model, we study a model where each player v tries to maximize the number of players at distance at most k from v, for a fixed parameter k. For example, when the network models friendship, then for k = 2, players would try to maximize the number of friends plus friends of their friends, which is an interesting metric in Sociology. We prove results on the structure and efficiency of such networks. In the final chapter, the network is fixed and each player chooses one of k colors. For example, the network might describe the spatial relations between the players and colors might correspond to radio frequencies, so each player’s aim is to choose a frequency that causes as few interference as possible with the frequencies of her neighbors

Second-Strike Nuclear Forces and Neorealist Theory: Unit-Level Challenge or Balance-of-Power Politics as Usual?

ABSTRACT: What are the implications of second-strike nuclear forces for neorealism? The end of the Cold War yielded a unipolar structure of international politics defined by the military, economic, and political preponderance of the United States. According to balance-of-power theory, which lies at the heart of neorealism, unipolarity has a short life span as secondary states waste little time in rectifying the global imbalance of power. Thus far, America remains unbalanced. Are we to take this as a refutation of balance-of-power theory? My thesis argues that second-strike arsenals render void the need to balance superior American military power. But because state survival is contingent not only upon military invulnerability (for which nuclear weapons are a sure guarantee), but also upon economic invulnerability (for which there is no absolute remedy), nuclear-weapon states are impelled to balance superior economic power for security reasons. By recasting balance-of-power theory in light of these assumptions, one can make sense of the great-power politics of the post-Cold War era.N/ADepartment of Government and International Relation

Dueling for honor and identity economics

Dueling is one of the best indicators of political transition from anarchy to order. This paper explores the dynamics of dueling for honor as a social institution in England, France, and Germany. It identifies major differences regarding the frequency, duration, and nature of dueling. Although dueling for honor emerged as a self-organizing and self-regulatory collective action of the aristocracy in crisis, it transformed into a middle class institution in France and Germany. However, this institution suddenly ended in England around 1850. In this study, we will follow a cognitive version of identity economics to explain the emergence of this institution, and its divergent trajectories in these countries in terms of identity choice. We will argue that while dueling is an identity investment, it might have different values according to its diverse social meanings. We will show that different social meanings that were attached to dueling in England, France and Germany gave rise to different values in identity investment, and led to different results in enhancing social identities

Restraining the Genuine Homo Economicus: Why the Economy Cannot be Divorced from its Governance

The Homo economicus of traditional economics is far from being completely self-interested, rational, or as individualistic as he is purported to be; he will haggle to death over price but will not take what he wants by force. Implicitly, he is assumed to behave ruthlessly within a welldefined bubble of sainthood. Based on a simple model, I first examine what occurs when this assumption is relaxed and genuine, amoral Homo economici interact. Productivity can be inversely related to compensation; a longer shadow of the future can intensify conflict; and, more competition among providers of protection reduces welfare. The patently inefficient outcomes that follow call for restraining self-interest, for finding ways to govern markets. I then review some of the different ways of creating restraints, from the traditional social contract, to the hierarchical domination of kings and lords, to modern forms of governance. Checks and balances, wider representation, the bureaucratic form of organization, and other ingredients of modern governance can partly be thought of as providing restraints to the dark side of self-interest. Though highly imperfect, these restraints are better than the alternative, which typically involves autocratic, amateurish, and corrupt rule. Then, thinking of most problems in terms of a first-best economic model is practically and scientifically misguided.

Strategic Network Formation with Attack and Immunization

Strategic network formation arises where agents receive benefit from connections to other agents, but also incur costs for forming links. We consider a new network formation game that incorporates an adversarial attack, as well as immunization against attack. An agent's benefit is the expected size of her connected component post-attack, and agents may also choose to immunize themselves from attack at some additional cost. Our framework is a stylized model of settings where reachability rather than centrality is the primary concern and vertices vulnerable to attacks may reduce risk via costly measures. In the reachability benefit model without attack or immunization, the set of equilibria is the empty graph and any tree. The introduction of attack and immunization changes the game dramatically; new equilibrium topologies emerge, some more sparse and some more dense than trees. We show that, under a mild assumption on the adversary, every equilibrium network with $n$ agents contains at most $2n-4$ edges for $n\geq 4$. So despite permitting topologies denser than trees, the amount of overbuilding is limited. We also show that attack and immunization don't significantly erode social welfare: every non-trivial equilibrium with respect to several adversaries has welfare at least as that of any equilibrium in the attack-free model. We complement our theory with simulations demonstrating fast convergence of a new bounded rationality dynamic which generalizes linkstable best response but is considerably more powerful in our game. The simulations further elucidate the wide variety of asymmetric equilibria and demonstrate topological consequences of the dynamics e.g. heavy-tailed degree distributions. Finally, we report on a behavioral experiment on our game with over 100 participants, where despite the complexity of the game, the resulting network was surprisingly close to equilibrium.Comment: The short version of this paper appears in the proceedings of WINE-1

THE ROLE OF GERMANY IN EUROPEAN SECURITY AFTER REUNIFICATION

The end of the Second World War brought a new kind of system and of stability in Europe that they never had experienced before. The war, occupation, and postwar European institutions transformed Germany profoundly both internally and externally by linking its foreign and security policy to multilateral frameworks. The new Germany is not a major military power like the old German empire, rather the most powerful civilian, economic and political actor that have the capability to influence policies in Europe and beyond without employing military power