Paper 2020/790

Anonymity and Rewards in Peer Rating Systems

Lydia Garms, Siaw-Lynn Ng, Elizabeth A. Quaglia, and Giulia Traverso

Abstract

When peers rate each other, they may choose to rate inaccurately in order to boost their own reputation or unfairly lower another’s. This could be successfully mitigated by having a reputation server incentivise accurate ratings with a reward. However, assigning rewards becomes a challenge when ratings are anonymous, since the reputation server cannot tell which peers to reward for rating accurately. To address this, we propose an anonymous peer rating system in which users can be rewarded for accurate ratings, and we formally define its model and security requirements. In our system ratings are rewarded in batches, so that users claiming their rewards only reveal they authored one in this batch of ratings. To ensure the anonymity set of rewarded users is not reduced, we also split the reputation server into two entities, the Rewarder, who knows which ratings are rewarded, and the Reputation Holder, who knows which users were rewarded. We give a provably secure construction satisfying all the security properties required. For our construction we use a modification of a Direct Anonymous Attestation scheme to ensure that peers can prove their own reputation when rating others, and that multiple feedback on the same subject can be detected. We then use Linkable Ring Signatures to enable peers to be rewarded for their accurate ratings, while still ensuring that ratings are anonymous. Our work results in a system which allows for accurate ratings to be rewarded, whilst still providing anonymity of ratings with respect to the central entities managing the system.

Metadata
Available format(s)
PDF
Category
Cryptographic protocols
Publication info
Published elsewhere. MAJOR revision.The Twelfth Conference on Security and Cryptography for Networks (SCN 2020)
Keywords
Linkable Ring SignaturesDirect Anonymous AttestationReputation SystemsIncentives
Contact author(s)
Lydia Garms @ rhul ac uk
History
2020-06-27: received
Short URL
https://ia.cr/2020/790
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2020/790,
      author = {Lydia Garms and Siaw-Lynn Ng and Elizabeth A.  Quaglia and Giulia Traverso},
      title = {Anonymity and Rewards in Peer Rating Systems},
      howpublished = {Cryptology ePrint Archive, Paper 2020/790},
      year = {2020},
      note = {\url{https://eprint.iacr.org/2020/790}},
      url = {https://eprint.iacr.org/2020/790}
}
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