Paper 2020/885

Wendy, the Good Little Fairness Widget

Klaus Kursawe


The advent of decentralized trading markets introduces a number of new challenges for consensus protocols. In addition to the 'usual' attacks - a subset of the validators trying to prevent disagreement -- there is now the possibility of financial fraud, which can abuse properties not normally considered critical in consensus protocols. We investigate the issues of attackers manipulating or exploiting the order in which transactions are scheduled in the blockchain. More concretely, we look into relative order fairness, i.e., ways we can assure that the relative order of transactions is fair. We show that one of the more intuitive definitions of fairness is impossible to achieve. We then present Wendy, a group of low overhead protocols that can implement different concepts of fairness. Wendy acts as an aditional widget for an existing blockchain, and is largely agnostic to the underlying blockchain and its security assumptions. Furthermore, it is possible to apply a the protocol only for a subset of the transactions, and thus run several independent fair markets on the same chain.

Available format(s)
Cryptographic protocols
Publication info
Preprint. MINOR revision.
BlockchainByzantine Fault ToleranceFrontrunning
Contact author(s)
klaus @ vega xyz
2020-07-16: received
Short URL
Creative Commons Attribution


      author = {Klaus Kursawe},
      title = {Wendy, the Good Little Fairness Widget},
      howpublished = {Cryptology ePrint Archive, Paper 2020/885},
      year = {2020},
      note = {\url{}},
      url = {}
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