Free-riding and whitewashing in peer-to-peer systems

Michal Feldman, Christos Papadimitriou, John Chuang, Ion Stoica

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


We develop a model to study the phenomenon of free-riding in peer-to-peer (P2P) systems. At the heart of our model is a user of a certain type, an intrinsic and private parameter that reflects the user's willingness to contribute resources to the system. A user decides whether to contribute or free-ride based on how the current contribution cost in the system compares to her type. When the societal generosity (i.e., the average type) is low, intervention is required in order to sustain the system. We present the effect of mechanisms that exclude low type users or, more realistic, penalize free-riders with degraded service. We also consider dynamic scenarios with arrivals and departures of users, and with whitewashers: users who leave the system and rejoin with new identities to avoid reputational penalties. We find that when penalty is imposed on all newcomers in order to avoid whitewashing, system performance degrades significantly only when the turnover rate among users is high.

Original languageEnglish
Title of host publicationProceedings of the ACM SIGCOMM 2004 Workshops
PublisherAssociation for Computing Machinery
Number of pages8
ISBN (Print)158113942X, 9781581139426
StatePublished - 2004
Externally publishedYes
EventProceedings of the ACM SIGCOMM 2004 Workshops - Portland, OR, United States
Duration: 30 Aug 20043 Sep 2004

Publication series

NameProceedings of the ACM SIGCOMM 2004 Workshops


ConferenceProceedings of the ACM SIGCOMM 2004 Workshops
Country/TerritoryUnited States
CityPortland, OR


  • Cheap pseudonyms
  • Cooperation
  • Equilibrium
  • Exclusion
  • Free-riding
  • Identity cost
  • Incentives
  • Peer-to-peer
  • Whitewashing


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