IPTPS '01 Revised Papers from the First International Workshop on Peer-to-Peer Systems
Vivaldi: a decentralized network coordinate system
Proceedings of the 2004 conference on Applications, technologies, architectures, and protocols for computer communications
Secure routing for structured peer-to-peer overlay networks
OSDI '02 Proceedings of the 5th symposium on Operating systems design and implementationCopyright restrictions prevent ACM from being able to make the PDFs for this conference available for downloading
Computational Puzzles as Sybil Defenses
P2P '06 Proceedings of the Sixth IEEE International Conference on Peer-to-Peer Computing
SybilGuard: defending against sybil attacks via social networks
Proceedings of the 2006 conference on Applications, technologies, architectures, and protocols for computer communications
Attacking a Swarm with a Band of Liars: evaluating the impact of attacks on BitTorrent
P2P '07 Proceedings of the Seventh IEEE International Conference on Peer-to-Peer Computing
SybilLimit: A Near-Optimal Social Network Defense against Sybil Attacks
SP '08 Proceedings of the 2008 IEEE Symposium on Security and Privacy
Protecting BitTorrent: Design and Evaluation of Effective Countermeasures against DoS Attacks
SRDS '08 Proceedings of the 2008 Symposium on Reliable Distributed Systems
Veracity: practical secure network coordinates via vote-based agreements
USENIX'09 Proceedings of the 2009 conference on USENIX Annual technical conference
NAT usage in residential broadband networks
PAM'11 Proceedings of the 12th international conference on Passive and active measurement
Uncovering social network sybils in the wild
Proceedings of the 2011 ACM SIGCOMM conference on Internet measurement conference
Efficient blacklisting and pollution-level estimation in p2p file-sharing systems
AINTEC'05 Proceedings of the First Asian Internet Engineering conference on Technologies for Advanced Heterogeneous Networks
Securing P2P systems from Sybil attacks through adaptive identity management
Proceedings of the 7th International Conference on Network and Services Management
Free-riding and whitewashing in peer-to-peer systems
IEEE Journal on Selected Areas in Communications
Building a reputation-based bootstrapping mechanism for newcomers in collaborative alert systems
Journal of Computer and System Sciences
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The Sybil attack consists on the indiscriminate creation of counterfeit identities, by a malicious user (attacker), in large-scale, dynamic distributed systems (for example, Peer-to-Peer). An effective approach to tackle this attack consists in establishing computational puzzles to be solved prior to granting new identities. Solutions based on this approach have the potential to slow down the assignment of identities to malicious users, but unfortunately may affect normal users as well. To address this problem, we propose the use of adaptive computational puzzles as an approach to limit the spread of Sybils. The key idea is to estimate a trust score of the source from which identity requests depart, calculated as a proportion of the number of identities already granted to (the) user(s) associated to that source, in regard to the average of identities granted to users associated to other sources. The higher the frequency (the) user(s) associated to a source obtain(s) identities, the lower the trust score of that source and, consequently, the higher the complexity of the puzzle to be solved. An in-depth analysis of both (i) the performance of our mechanism under various parameter and environment settings, and (ii) the results achieved with an experimental evaluation, considering real-life traces from a Peer-to-Peer file sharing community, has shown the effectiveness of the proposed mechanism in limiting the spread of Sybil identities. While comparatively more complex puzzles were assigned to potential attackers, legitimate users were minimally penalized with easier-to-solve puzzles.