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

Mingyu Liang, Ioanna Karantaidou, Foteini Baldimtsi, 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.

Available format(s)
Category
Cryptographic protocols
Publication info
Published elsewhere. Proceedings on Privacy Enhancing Technologies 2022 Issue 1
Keywords
Anonymous MixingCryptocurrencyDifferential Privacy
Contact author(s)
mliang5 @ gmu edu
ikaranta @ gmu edu
foteini @ gmu edu
gordon @ gmu edu
varia @ bu edu
History
Short URL
https://ia.cr/2021/1197

CC BY

BibTeX

@misc{cryptoeprint:2021/1197,
author = {Mingyu Liang and Ioanna Karantaidou and Foteini Baldimtsi and Dov Gordon and Mayank Varia},
title = {($\epsilon,\delta$)-indistinguishable Mixing for Cryptocurrencies},
howpublished = {Cryptology ePrint Archive, Paper 2021/1197},
year = {2021},
note = {\url{https://eprint.iacr.org/2021/1197}},
url = {https://eprint.iacr.org/2021/1197}
}

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