Dragoon: Private decentralized hits made practical

Yuan Lu, Qiang Tang, Guiling Wang

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Scopus citations


—With the rapid popularity of blockchain, decentralized human intelligence tasks (HITs) are proposed to crowdsource human knowledge without relying on vulnerable third-party platforms. However, the inherent limits of blockchain cause decentralized HITs to face a few “new” challenges. For example, the confidentiality of solicited data turns out to be the sine qua non, though it was an arguably dispensable property in the centralized setting. To ensure the “new” requirement of data privacy, existing decentralized HITs use generic zero-knowledge proof frameworks (e.g., SNARK), but scarcely perform well in practice, due to the inherently expensive cost of generality. We present a practical decentralized protocol for HITs, which also achieves the fairness between requesters and workers. At the core of our contributions, we avoid the powerful yet highly-costly generic zk-proof tools and propose a special-purpose scheme to prove the quality of encrypted data. By various nontrivial statement reformations, proving the quality of encrypted data is reduced to efficient verifiable decryption, thus making decentralized HITs practical. Along the way, we rigorously define the ideal functionality of decentralized HITs and then prove the security due to the ideal/real paradigm. We further instantiate our protocol to implement a system called Dragoon1, an instance of which is deployed atop Ethereum to facilitate an image annotation task used by ImageNet. Our evaluations demonstrate its practicality: the on-chain handling cost of Dragoon is even less than the handling fee of Amazon’s Mechanical Turk for the same ImageNet HIT.

Original languageEnglish (US)
Title of host publicationProceedings - 2020 IEEE 40th International Conference on Distributed Computing Systems, ICDCS 2020
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages11
ISBN (Electronic)9781728170022
StatePublished - Nov 2020
Event40th IEEE International Conference on Distributed Computing Systems, ICDCS 2020 - Singapore, Singapore
Duration: Nov 29 2020Dec 1 2020

Publication series

NameProceedings - International Conference on Distributed Computing Systems


Conference40th IEEE International Conference on Distributed Computing Systems, ICDCS 2020

All Science Journal Classification (ASJC) codes

  • Software
  • Hardware and Architecture
  • Computer Networks and Communications


  • Blockchain
  • Decentralized application
  • Human intelligence task
  • crowdsourcing


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