Auctions, Market Mechanisms and Their Applications. First International ICST Conference, AMMA 2009, Boston, MA, USA, May 8-9, 2009, Revised Selected Papers

Research Article

Manipulating Scrip Systems: Sybils and Collusion

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  • @INPROCEEDINGS{10.1007/978-3-642-03821-1_4,
        author={Ian Kash and Eric Friedman and Joseph Halpern},
        title={Manipulating Scrip Systems: Sybils and Collusion},
        proceedings={Auctions, Market Mechanisms and Their Applications. First International ICST Conference, AMMA 2009, Boston, MA, USA, May 8-9, 2009, Revised Selected Papers},
        proceedings_a={AMMA},
        year={2012},
        month={5},
        keywords={},
        doi={10.1007/978-3-642-03821-1_4}
    }
    
  • Ian Kash
    Eric Friedman
    Joseph Halpern
    Year: 2012
    Manipulating Scrip Systems: Sybils and Collusion
    AMMA
    Springer
    DOI: 10.1007/978-3-642-03821-1_4
Ian Kash1,*, Eric Friedman1,*, Joseph Halpern1,*
  • 1: Cornell University
*Contact email: kash@cs.cornell.edu, ejf27@cornell.edu, halpern@cs.cornell.edu

Abstract

Game-theoretic analyses of distributed and peer-to-peer systems typically use the Nash equilibrium solution concept, but this explicitly excludes the possibility of strategic behavior involving more than one agent. We examine the effects of two types of strategic behavior involving more than one agent, sybils and collusion, in the context of scrip systems where agents provide each other with service in exchange for scrip. Sybils make an agent more likely to be chosen to provide service, which generally makes it harder for agents without sybils to earn money and decreases social welfare. Surprisingly, in certain circumstances it is possible for sybils to make all agents better off. While collusion is generally bad, in the context of scrip systems it actually tends to make all agents better off, not merely those who collude. These results also provide insight into the effects of allowing agents to advertise and loan money.