Cryptology ePrint Archive: Report 2021/1197

($\epsilon,\delta$)-indistinguishable Mixing for Cryptocurrencies

Mingyu Liang and Ioanna Karantaidou and Foteini Baldimtsi and Dov Gordon and Mayank Varia

Abstract: We propose a new theoretical approach for building anonymous mixing mechanisms for cryptocurrencies. Rather than requiring a fully uniform permutation during mixing, we relax the requirement, insisting only that neighboring permutations are similarly likely. This is defined formally by borrowing from the definition of differential privacy. This relaxed privacy definition allows us to greatly reduce the amount of interaction and computation in the mixing protocol. Our construction achieves $O(n \cdot polylog(n))$ computation time for mixing $n$ addresses, whereas all other mixing schemes require $O(n^2)$ total computation across all parties. Additionally, we support a smooth tolerance of fail-stop adversaries and do not require any trusted setup. We analyze the security of our generic protocol under the UC framework, and under a stand-alone, game-based definition. We finally describe an instantiation using ring signatures and confidential transactions.

Category / Keywords: cryptographic protocols / Anonymous Mixing, Cryptocurrency, Differential Privacy

Original Publication (in the same form): Proceedings on Privacy Enhancing Technologies 2022 Issue 1

Date: received 15 Sep 2021, last revised 15 Sep 2021

Contact author: mliang5 at gmu edu, ikaranta at gmu edu, foteini at gmu edu, gordon at gmu edu, varia at bu edu

Available format(s): PDF | BibTeX Citation

Version: 20210917:091506 (All versions of this report)

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