Paper 2023/144

Aegis: Privacy-Preserving Market for Non-Fungible Tokens

Hisham S. Galal, Assiut University
Amr M. Youssef, Concordia University

Non-fungible tokens (NFTs) are unique non-interchangeable digital assets verified and stored using blockchain technology. Quite recently, there has been a surging interest and adoption of NFTs, with sales exceeding \$10 billion in the third quarter of 2021. Given the public state of Blockchain, NFTs owners face a privacy problem. More precisely, an observer can trivially learn the whole NFT collections owned by an address. For some categories of NFTs like arts and game collectibles, owners can sell them for a profit. However, popular marketplaces trade NFTs using public auctions and direct offers. Hence, an observer can learn about the new owner and the NFT purchase price. To tackle those problems, we propose Aegis, a protocol that allows users to add privacy to their NFTs ownership. In Aegis, users can swap NFTs for payment amounts in fungible tokens while hiding the details (i.e., involved parties, the NFTs, and the payment amounts). One of the main properties of Aegis is its complete compatibility with existing NFT standards. We design Aegis by leveraging a zk-SNARK proof system and smart contracts. We build an open-source prototype and perform experiments to evaluate Aegis's performance.

Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. IEEE Transactions on Network Science and Engineering
Contact author(s)
hisham_sg @ aun edu eg
youssef @ ciise concordia ca
2023-02-15: approved
2023-02-07: received
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Short URL
Creative Commons Attribution-NonCommercial


      author = {Hisham S. Galal and Amr M. Youssef},
      title = {Aegis: Privacy-Preserving Market for Non-Fungible Tokens},
      howpublished = {Cryptology ePrint Archive, Paper 2023/144},
      year = {2023},
      doi = {10.1109/TNSE.2022.3205428},
      note = {\url{}},
      url = {}
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