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124
Strong Price of Anarchy
"... A strong equilibrium (Aumann 1959) is a pure Nash equilibrium which is resilient to deviations by coalitions. We define the strong price of anarchy to be the ratio of the worst case strong equilibrium to the social optimum. In contrast to the traditional price of anarchy, which quantifies the loss i ..."
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Cited by 73 (10 self)
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A strong equilibrium (Aumann 1959) is a pure Nash equilibrium which is resilient to deviations by coalitions. We define the strong price of anarchy to be the ratio of the worst case strong equilibrium to the social optimum. In contrast to the traditional price of anarchy, which quantifies the loss incurred due to both selfishness and lack of coordination, the strong price of anarchy isolates the loss originated from selfishness from that obtained due to lack of coordination. We study the strong price of anarchy in two settings, one of job scheduling and the other of network creation. In the job scheduling game we show that for unrelated machines the strong price of anarchy can be bounded as a function of the number of machines and the size of the coalition. For the network creation game we show that the strong price of anarchy is at most 2. In both cases we show that a strong
FlightPath: Obedience vs choice in cooperative services
 In OSDI 2008
, 2008
"... Abstract: We present FlightPath, a novel peertopeer streaming application that provides a highly reliable data stream to a dynamic set of peers. We demonstrate that FlightPath reduces jitter compared to previous works by several orders of magnitude. Furthermore, FlightPath uses a number of runtim ..."
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Cited by 50 (7 self)
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Abstract: We present FlightPath, a novel peertopeer streaming application that provides a highly reliable data stream to a dynamic set of peers. We demonstrate that FlightPath reduces jitter compared to previous works by several orders of magnitude. Furthermore, FlightPath uses a number of runtime adaptations to maintain low jitter despite 10 % of the population behaving maliciously and the remaining peers acting selfishly. At the core of FlightPath’s success are approximate equilibria. These equilibria allow us to design incentives to limit selfish behavior rigorously, yet they provide sufficient flexibility to build practical systems. We show how to use an εNash equilibrium, instead of a strict Nash, to engineer a live streaming system that uses bandwidth efficiently, absorbs flash crowds, adapts to sudden peer departures, handles churn, and tolerates malicious activity. 1
Rational Secret Sharing, Revisited
 IN SCN (SECURITY IN COMMUNICATION NETWORKS)
, 2006
"... We consider the problem of secret sharing among n rational players. This problem was introduced by Halpern and Teague (STOC 2004), who claim that a solution is impossible for n = 2 but show a solution for the case n >= 3. Contrary to their claim, we show a protocol for rational secret sharing ..."
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Cited by 49 (4 self)
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We consider the problem of secret sharing among n rational players. This problem was introduced by Halpern and Teague (STOC 2004), who claim that a solution is impossible for n = 2 but show a solution for the case n >= 3. Contrary to their claim, we show a protocol for rational secret sharing among n = 2 players; our protocol extends to the case n 3, where it is simpler than the HalpernTeague solution and also o#ers a number of other advantages. We also show how to avoid the continual involvement of the dealer, in either our own protocol or that of Halpern and Teague. Our
Bridging Game Theory and Cryptography: Recent Results and Future Directions
"... Abstract. Motivated by the desire to develop more realistic models of, and protocols for, interactions between mutually distrusting parties, there has recently been significant interest in combining the approaches and techniques of game theory with those of cryptographic protocol design. Broadly spe ..."
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Cited by 40 (3 self)
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Abstract. Motivated by the desire to develop more realistic models of, and protocols for, interactions between mutually distrusting parties, there has recently been significant interest in combining the approaches and techniques of game theory with those of cryptographic protocol design. Broadly speaking, two directions are currently being pursued: Applying cryptography to game theory: Certain gametheoretic equilibria are achievable if a trusted mediator is available. The question here is: to what extent can this mediator be replaced by a distributed cryptographic protocol run by the parties themselves? Applying gametheory to cryptography: Traditional cryptographic models assume some honest parties who faithfully follow the protocol, and some arbitrarily malicious players against whom the honest players must be protected. Gametheoretic models propose instead that all players are simply selfinterested (i.e., rational), and the question then is: how can we model and design meaningful protocols for such a setting? In addition to surveying known results in each of the above areas, I suggest some new definitions along with avenues for future research. 1
Cryptography and game theory: Designing protocols for exchanging information
 In Theory of Cryptography Conference
, 2008
"... The goal of this paper is nding fair protocols for the secret sharing and secure multiparty computation (SMPC) problems, when players are assumed to be rational. It was observed by Halpern and Teague (STOC 2004) that protocols with bounded number of iterations are susceptible to backward induction a ..."
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Cited by 40 (1 self)
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The goal of this paper is nding fair protocols for the secret sharing and secure multiparty computation (SMPC) problems, when players are assumed to be rational. It was observed by Halpern and Teague (STOC 2004) that protocols with bounded number of iterations are susceptible to backward induction and cannot be considered rational. Previously suggested cryptographic solutions all share the property of having an essential exponential upper bound on their running time, and hence they are also susceptible to backward induction. Although it seems that this bound is an inherent property of every cryptography based solution, we show that this is not the case. We suggest coalitionresilient secret sharing and SMPC protocols with the property that after any sequence of iterations it is still a computational best response to follow them. Therefore, the protocols can be run any number of iterations, and are immune to backward induction. The mean of communication assumed is a broadcast channel, and we consider both the simultaneous and nonsimultaneous cases.
Rationality and adversarial behavior in multiparty computation
 Advances in Cryptology — Crypto 2006
, 2006
"... Abstract. We study multiparty computation in the model where none of n participating parties are honest: they are either rational, acting in their selfish interest to maximize their utility, or adversarial, acting arbitrarily. In this new model, which we call the mixedbehavior model, we define a c ..."
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Cited by 39 (1 self)
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Abstract. We study multiparty computation in the model where none of n participating parties are honest: they are either rational, acting in their selfish interest to maximize their utility, or adversarial, acting arbitrarily. In this new model, which we call the mixedbehavior model, we define a class of functions that can be computed in the presence of an adversary using a trusted mediator. We then give a protocol that allows the rational parties to emulate the mediator and jointly compute the function such that (1) assuming that each rational party prefers that it learns the output while others do not, no rational party has an incentive to deviate from the protocol; and (2) the rational parties are protected from a malicious adversary controlling ⌈ n ⌉ − 2 of the participants: the 2 adversary can only either cause all rational participants to abort (so no one learns the function they are trying to compute), or can only learn whatever information is implied by the output of the function. 1
Game Theory Meets Network Security and Privacy
"... This survey provides a structured and comprehensive overview of the research contributions that analyze and solve security and privacy problems in computer networks by gametheoretic approaches. A selected set of works are presented to highlight the application of game theory in order to address dif ..."
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Cited by 35 (5 self)
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This survey provides a structured and comprehensive overview of the research contributions that analyze and solve security and privacy problems in computer networks by gametheoretic approaches. A selected set of works are presented to highlight the application of game theory in order to address different forms of security and privacy problems in computer networks and mobile applications. The presented works are classified into six main categories based on their topics: security of the physical and MAC layers, application layer security in mobile networks, intrusion detection systems, anonymity and privacy, economics of network security, and cryptography. In each category, security problems, players, and game models are identified and the main results of selected works, such as equilibrium analysis and security mechanism designs are summarized. In addition, a discussion on advantages, drawbacks, and the future direction of using game theory in this field is provided. In this survey, we aim to provide a better understanding of the different research approaches for applying game theory to network security. This survey can also help researchers from various fields develop gametheoretic solutions to current and emerging security problems in computer networking. Categories and Subject Descriptors: C.2.0 [ComputerCommunication Networks]: General—
Strong Mediated Equilibrium
 In Proceedings of AAAI06
, 2006
"... Providing agents with strategies that will be robust against deviations by coalitions is central to the design of multiagent agents. However, such strategies, captured by the notion of strong equilibrium, rarely exist. This paper suggests the use of mediators in order to enrich the set of situati ..."
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Cited by 30 (5 self)
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Providing agents with strategies that will be robust against deviations by coalitions is central to the design of multiagent agents. However, such strategies, captured by the notion of strong equilibrium, rarely exist. This paper suggests the use of mediators in order to enrich the set of situations where we can obtain stability against deviations by coalitions. A mediator is a reliable entity, which can ask the agents for the right to play on their behalf, and is guaranteed to behave in a prespecified way based on messages received from the agents. However, a mediator can not enforce behavior; that is, ∗ An extended abstract of this paper is appearing at the TwentyFirst National Conference on Artificial Intelligence (AAAI06). Almost all proofs are missing from the extended abstract. This Version of the paper contains all of these missing proofs, and provides additional discussions and results. Furthermore, some of the definitions that do appear in the extended abstract have been slightly modified. 1 agents can play in the game directly without the mediator’s help. We prove some general results about mediators, and concentrate on the notion of strong mediated equilibrium; we show that desired behaviors, which are stable against deviations by coalitions, can be obtained using mediators in several class of settings. 1
Lower bounds on implementing robust and resilient mediators
, 2007
"... We consider games that have (k, t)robust equilibria when played with a mediator, where an equilibrium is (k, t)robust if it tolerates deviations by coalitions of size up to k and deviations by up to t players with unknown utilities. We prove lower bounds that match upper bounds on the ability to i ..."
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Cited by 28 (7 self)
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We consider games that have (k, t)robust equilibria when played with a mediator, where an equilibrium is (k, t)robust if it tolerates deviations by coalitions of size up to k and deviations by up to t players with unknown utilities. We prove lower bounds that match upper bounds on the ability to implement such mediators using cheap talk (that is, just allowing communication among the players). The bounds depend on (a) the relationship between k, t and n, the total number of players in the system; (b) whether players know the exact utilities of other players; (c) whether there are broadcast channels or just pointtopoint channels; (d) whether cryptography is available; and (e) whether the game has a (k + t)punishment strategy; that is, a strategy that, if used by all but at most k + t players, guarantees that every player gets a worse outcome than they do with the equilibrium strategy.
Efficient rational secret sharing in standard communication networks
 In TCC
, 2010
"... We propose a new methodology for rational secret sharing leading to various instantiations (in both the twoparty and multiparty settings) that are simple and efficient in terms of computation, share size, and round complexity. Our protocols do not require physical assumptions or simultaneous chann ..."
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Cited by 25 (2 self)
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We propose a new methodology for rational secret sharing leading to various instantiations (in both the twoparty and multiparty settings) that are simple and efficient in terms of computation, share size, and round complexity. Our protocols do not require physical assumptions or simultaneous channels, and can even be run over asynchronous, pointtopoint networks. We also propose new equilibrium notions (namely, computational versions of strict Nash equilibrium and stability with respect to trembles) and prove that our protocols satisfy them. These notions guarantee, roughly speaking, that at each point in the protocol there is a unique legal message a party can send. This, in turn, ensures that protocol messages cannot be used as subliminal channels, something achieved in prior work only by making strong assumptions on the communication network. 1