A Formal Analysis of Syverson`s Rational Exchange Protocol

In this paper, we provide a formal analysis of a rational exchange protocol proposed by Syverson. A rational exchange protocol guarantees that misbehavior cannot generate benefits, and is therefore discouraged. The analysis is performed using our formal model, which is based on game theory. In this model, rational exchange is defined in terms of a Nash equilibrium

A Formal Model of Rational Exchange and Its Application to the Analysis of Syverson's Protocol

We propose a formal model of rational exchange and exchange protocols in general, which is based on game theory. In this model, an exchange protocol is represented as a set of strategies in a game that is played by the protocol parties and the network that they use to communicate with each other. Within this model, we give a formal definition for rational exchange and various other properties of exchange protocols, including fairness. In particular, rational exchange is defined in terms of a Nash equilibrium in the protocol game. We also study the relationship between rational and fair exchange, and prove that fairness implies rationality, but not vice versa. Finally, we illustrate the usage of our formal model for the analysis of existing rational exchange protocols by analyzing a protocol proposed by Syverson. We show that the protocol is rational only under the assumption that the network is reliable

Building blocks for secure services:authenticated key transport and rational exchange protocols

This thesis is concerned with two security mechanisms: authenticated key transport and rational exchange protocols. These mechanisms are potential building blocks in the security architecture of a range of different services. Authenticated key transport protocols are used to build secure channels between entities, which protect their communications against eaves-dropping and alteration by an outside attacker. In contrast, rational exchange protocols can be used to protect the entities involved in an exchange transaction from each other. This is important, because often the entities do not trust each other, and both fear that the other will gain an advantage by misbehaving. Rational exchange protocols alleviate this problem by ensuring that a misbehaving party cannot gain any advantages. This means that misbehavior becomes uninteresting and it should happen only rarely. The thesis is focused on the construction of formal models for authenticated key transport and rational exchange protocols. In the first part of the thesis, we propose a formal model for key transport protocols, which is based on a logic of belief. Building on this model, we also propose an original systematic protocol construction approach. The main idea is that we reverse some implications that can be derived from the axioms of the logic, and turn them into synthesis rules. The synthesis rules can be used to construct a protocol and to derive a set of assumptions starting from a set of goals. The main advantage is that the resulting protocol is guaranteed to be correct in the sense that all the specified goals can be derived from the protocol and the assumptions using the underlying logic. Another important advantage is that all the assumptions upon which the correctness of the protocol depends are made explicit. The protocol obtained in the synthesis process is an abstract protocol, in which idealized messages that contain logical formulae are sent on channels with various access properties. The abstract protocol can then be implemented in several ways by replacing the idealized messages and the channels with appropriate bit strings and cryptographic primitives, respectively. We illustrate the usage of the logic and the synthesis rules through an example: We analyze an authenticated key transport protocol proposed in the literature, identify several weaknesses, show how these can be exploited by various attacks, and finally, we redesign the protocol using the proposed systematic approach. We obtain a protocol that resists against the presented attacks, and in addition, it is simpler than the original one. In the second part of the thesis, we propose an original formal model for exchange protocols, which is based on game theory. In this model, an exchange protocol is represented as a set of strategies in a game played by the protocol parties and the network that they use to communicate with each other. We give formal definitions for various properties of exchange protocols in this model, including rationality and fairness. Most importantly, rationality is defined in terms of a Nash equilibrium in the protocol game. The model and the formal definitions allow us to rigorously study the relationship between rational exchange and fair exchange, and to prove that fairness implies rationality (given that the protocol satisfies some further usual properties), but the reverse is not true in general. We illustrate how the formal model can be used for rigorous verification of existing protocols by analyzing two exchange protocols, and formally proving that they satisfy the definition of rational exchange. We also present an original application of rational exchange: We show how the concept of rationality can be used to improve a family of micropayment schemes with respect to fairness without substantial loss in efficiency. Finally, in the third part of the thesis, we extend the concept of rational exchange, and describe how similar ideas can be used to stimulate the nodes of a self-organizing ad hoc network for cooperation. More precisely, we propose an original approach to stimulate the nodes for packet forwarding. Like in rational exchange protocols, our design does not guarantee that a node cannot deny packet forwarding, but it ensures that it cannot gain any advantages by doing so. We analyze the proposed solution analytically and by means of simulation

A Rational Approach to Cryptographic Protocols

This work initiates an analysis of several cryptographic protocols from a rational point of view using a game-theoretical approach, which allows us to represent not only the protocols but also possible misbehaviours of parties. Concretely, several concepts of two-person games and of two-party cryptographic protocols are here combined in order to model the latters as the formers. One of the main advantages of analysing a cryptographic protocol in the game-theory setting is the possibility of describing improved and stronger cryptographic solutions because possible adversarial behaviours may be taken into account directly. With those tools, protocols can be studied in a malicious model in order to find equilibrium conditions that make possible to protect honest parties against all possible strategies of adversaries

Tradition as a Communication System. A Pragmatic Approach

A context of my paper is the debate on reason, tradition and traditional communities, in which this moral and epistemological issues were discussed as a part of general socio-philosophical theory of modernity. In particular I intend to locate my considerations in the context of formal-pragmatic theory of modern communicative rationality developed by Jürgen Habermas and Robert Brandom. I will provide a competitive model of the rationality of tradition by applying a conceptual toolkit of pragmatically oriented analysis to explain practices connected with vocabulary of tradition. I argue that tradition as a communication system has a fully rational structure. My main claim is that communicative structure of tradition has a rational structure of language game. This structure includes defined principles of communication for members of closed tradition-grounded community and rule of inclusion for potential new members. Firstly I consider closely internal principles of communication within the framework of tradition contrasting them shortly with normative-deontic rules of the postenlightenment idea of pragmatic communication discussed by Jürgen Habermas and Robert Brandom. After that I examine the rule of inclusion — the rule, which mediates between closed system of tradition-based community and his environment.Numer został przygotowany przy wsparciu Ministerstwa Nauki i Szkolnictwa Wyższego

Human-Agent Decision-making: Combining Theory and Practice

Extensive work has been conducted both in game theory and logic to model strategic interaction. An important question is whether we can use these theories to design agents for interacting with people? On the one hand, they provide a formal design specification for agent strategies. On the other hand, people do not necessarily adhere to playing in accordance with these strategies, and their behavior is affected by a multitude of social and psychological factors. In this paper we will consider the question of whether strategies implied by theories of strategic behavior can be used by automated agents that interact proficiently with people. We will focus on automated agents that we built that need to interact with people in two negotiation settings: bargaining and deliberation. For bargaining we will study game-theory based equilibrium agents and for argumentation we will discuss logic-based argumentation theory. We will also consider security games and persuasion games and will discuss the benefits of using equilibrium based agents.Comment: In Proceedings TARK 2015, arXiv:1606.0729

Nashbots: How Political Scientists have Underestimated Human Rationality, and How to Fix It

Political scientists use experiments to test the predictions of game-theoretic models. In a typical experiment, each subject makes choices that determine her own earnings and the earnings of other subjects, with payments corresponding to the utility payoffs of a theoretical game. But social preferences distort the correspondence between a subject’s cash earnings and her subjective utility, and since social preferences vary, anonymously matched subjects cannot know their opponents’ preferences between outcomes, turning many laboratory tasks into games of incomplete information. We reduce the distortion of social preferences by pitting subjects against algorithmic agents (“Nashbots”). Across 11 experimental tasks, subjects facing human opponents played rationally only 36% of the time, but those facing algorithmic agents did so 60% of the time. We conclude that experimentalists have underestimated the economic rationality of laboratory subjects by designing tasks that are poor analogies to the games they purport to test

Institutional theory and legislatures

Institutionalism has become one of the dominant strands of theory within contemporary political science. Beginning with the challenge to behavioral and rational choice theory issued by March and Olsen, institutional analysis has developed into an important alternative to more individualistic approaches to theory and analysis. This body of theory has developed in a number of ways, and perhaps the most commonly applied version in political science is historical institutionalism that stresses the importance of path dependency in shaping institutional behaviour. The fundamental question addressed in this book is whether institutionalism is useful for the various sub-disciplines within political science to which it has been applied, and to what extent the assumptions inherent to institutional analysis can be useful for understanding the range of behavior of individuals and structures in the public sector. The volume will also examine the relative utility of different forms of institutionalism within the various sub-disciplines. The book consists of a set of strong essays by noted international scholars from a range of sub-disciplines within the field of political science, each analyzing their area of research from an institutionalist perspective and assessing what contributions this form of theorizing has made, and can make, to that research. The result is a balanced and nuanced account of the role of institutions in contemporary political science, and a set of suggestions for the further development of institutional theory

Constructivist and Ecological Rationality in Economics

When we leave our closet, and engage in the common affairs of life, (reason's) conclusions seem to vanish, like the phantoms of the night on the appearance of the morning; and 'tis difficult for us to retain even that conviction, which we had attained with difficulty (Hume, 1739/, p 507). we must constantly adjust our lives, our thoughts and our emotions, in order to live simultaneously within different kinds of orders according to different rules. If we were to apply the unmodified, uncurbed rules (of caring intervention to do visible 'good') of the small band or troop, or our families to the (extended order of cooperation through markets), as our instincts and sentimental yearnings often make us wish to do, we would destroy it. Yet if we were to always apply the (noncooperative) rules of the extended order to our more intimate groupings, we would crush them. (Hayek, 1988, p 18). (Italics are his, parenthetical reductions are mine).behavioral economics; experimental economics